How-To Geek

How to Convert PDF Files for Easy Ebook Reading


Many ebook readers natively support PDF documents but, unfortunately, not all PDF documents are easy to read on a small ebook reader screen. Let’s take a look at two simple and free ways to convert PDF files for enjoyable reading.

Kindles, Nooks, Sony Pocket Readers, and other popular readers support native PDF rendering. The problem with native rendering, however, is that many PDF documents are formatted to be read on a large screen or printed and read in hard copy. Large margins, multiple columns, and other formatting choices that aren’t such a big deal when the document in printed on 8.5×11 paper or displayed on a 20” monitor render the document almost unreadable when loaded into an e-reader with a 6” screen. Today we’re going to look at two ways you can re-format a PDF file for enjoyable reading on your favorite reader.

What You’ll Need

For our tutorial you’ll need the following things:

  • A copy of ebook management software Calibre.
  • A copy of K2pdfopt.
  • A PDF file to convert.
  • An e-reader to try the file out on.

We suggest keep a clean copy of your PDF test file in a separate directory so if all your conversion attempts go awry you’ll have the original safe and sound.

Converting Using Calibre2011-08-02_144256

Calibre is an awesome and open source ebook management tool. If you’ve read this far and have no intention of even mucking around with any PDF files you should go and download it regardless. It’s a fantastic tool for managing ebooks and ebook readers. What we’re interested in, book management aside, is the conversion tool built into Calibre.

If you’re totally new to using Calibre and need help installing it and getting your books into it, check out one of our previous Calibre-based guides to get started. Once you’ve installed it and you’ve loaded up a book you want to convert it’s time to get converting.

For our example we’ll be using a particularly complex textbook (multiple columns, charts, graphic headers for each chapter, etc.) and a Kindle. First let’s look at what the original PDF file looks like on the Kindle screen.


That’s eye-squintingly small on a large monitor screen and nearly illegible on a Kindle screen. There’s no way we could comfortable read that on a 6” kindle screen without serious eye strain and a headache. Let’s see if we can convert it with Calibre.

Open Calibre and right click on the book. Select Convert Books –> Convert individually. Here you’ll find an enormously detailed menu with toggles and settings galore. It’s easy to get overwhelmed and some of the settings are pretty arcane if you’re unfamiliar with printing terms and/or search string expressions. For the first conversion stick with the default settings and convert between PDF and a suitable format for your ebook reader or even PDF to PDF to restructure multi-column PDF files into a more streamlined document.

When it’s done converting you can check the formatting on your computer by double clicking on the converted file in the right hand book information column or you can transfer it to your device. We transferred it to the device to get a real sense of how it looked on the page.


Although we’ve used Calibre to convert hundreds of ebooks over the last few years with very few problems this particular PDF file proved to be a real challenge for it. The multiple columns, odd formatting choices, and other factors really stumped Calibre.

While Calibre normally does a fine job converting PDF files we picked one of the most difficult to convert PDFs we had on hand to demonstrate that things don’t always go as planned. We also picked a really hard to convert PDF so that we could in turn show off the next tool in our tutorial, K2pdfopt. It’s like the nuclear option when the normally reliable Calibre fails to crank out a working conversion.  If you find yourself in a similar boat, your complex PDF document didn’t turn out right, you’ll likely be thrilled with K2pdfopt.

Converting Optimizing PDF files using K2pdfopt


First, we want to give a big thanks to Abhijeet at Guiding Tech; we’d been looking for a tool like this and he tipped us off at just the right time. K2pdfopt is designed to optimize PDF documents for small screen e-readers. Rather than convert the document into raw text and try to reformat it, it instead carefully crops and realigns the pieces as though they were a series of images. The end result is a new PDF file that is really true to the original document and free from odd OCR blunders (as it doesn’t attempt to convert or reflow the text).

Using K2pdfopt is a snap. Extract the executable into a folder, drag a PDF file onto the EXE and let it work—as seen in the screenshot above. We dropped the same difficult to format textbook PDF into K2pdfopt and crossed our fingers. Given how much Calibre struggled with the document we weren’t sure what to expect. When the conversion completed (you’ll see a copy of your PDF file with the file named annotated like filename_k2opt.pdf in the K2pdfopt folder) we copied it over to our Kindle and were shocked at how well it handled the complex text we threw at it. page2

The text is slightly less crisp than in our PDF to MOBI conversion (see the screen capture in the Calibre section) but it is all there, with proper formatting, and without any screwy OCR errors. Thanks to K2pdfopt we went from having a PDF that was illegible on the Kindle to having a PDF that was as easy to read as a clean photocopy.

The only downside we could find in using K2pdfopt was the increase in file size. A 15MB PDF file, when converted with K2pdfopt, ballooned to 93MB. When you consider how few conversions Calibre doesn’t properly handle and how few books we’d need to actually send through the K2pdfopt image-based conversion process, though, it’s not a bad trade off. We can stand to increase the file size on a few PDFs in order to gain access to a portable and easily read copy.

Update: Shortly after this article went live on the site Marcus wrote in and asked

What if you took the K2pdfopt.exe output and ran the resulting PDF through Calibre again to convert it to a MOBI or ePUB? Maybe that would stop Calibre from choking on the multi-column format since it would now be formatted more like a standard book. Could you guys try it out?

What if, Marcus? What if, indeed. We dove in deeper, Inception-style, and performed a test just as you requested. Calibre handled the conversion beautifully and the text cleaned up perfectly. How perfectly? Here’s a snippet of the text seen in the screenshot above (which is properly formatted but a little grainy) after the reconversion process:

And there you have it. For a particularly tricky PDF file you can run it through K2pdfopt.exe, then dump it back into Calibre for a cleanup pass (check out how smooth the font is now in the above sample), and enjoy a totally optimized PDF. Good call, Marcus! The extra step only adds a few minutes to the process and really tidies things up.

Have a conversion tip, trick, or tool to share? We’re interested to hear about it so shoot us an email at or sound off about it in the comments here.



Jason Fitzpatrick is a warranty-voiding DIYer who spends his days cracking opening cases and wrestling with code so you don't have to. If it can be modded, optimized, repurposed, or torn apart for fun he's interested (and probably already at the workbench taking it apart). You can follow him on if you'd like.

  • Published 08/2/11

Comments (33)

  1. Chris

    What options are there for linux (Ubuntu) users?

    I love articles like thisobe; only problem is, author assumes everyone is using Windows.

  2. Chris

    Scratch that, I now see Calibre is available for linux too ^_^

  3. Jason Fitzpatrick

    Both Calibre and K2pdfopt are Windows/Linux compatible. =)

  4. Atomsk

    Nice I’ve been looking for something like this for my NC!

  5. Taylor

    When you convert a file to the same file format in current Calibre, it backs up the original in case things go bad. Just FTR.

  6. Screwtape

    Awesome guide. This should work great on my Nook simple reader.

  7. MeMechant

    Can someone help with linux installation of k2pdfopt ?

  8. rockson

    thanks, i was using Calibre with my nook, it works well with ‘text book’ like fiction and non-fiction.
    However, converting tools book like programming book had been bugging me for a long time. This kinda book simple carry a lot of table and figure, worst of all, the CODE example itself!! straight converting from PDF to epub just not readable. I am testing out papercrop lately, it is kinda working, but all the bookmarks and chapter layout will be gone after the convertion. SO~~ anything good suggestion??? thanks in advance

  9. Ankur

    its totally illegible after conversion . text is not clear. so whole point of doing this is waste

  10. davidh4976

    There are online conversions sites that work reasonably well. I’ve used Google convert to epub to get other options.

  11. Karl K

    What a godsend! K2PDF is just what the calibre/Kindle world needs! Many thanks!

    Some notes on your article:
    1. The folks at calibre INSIST on it being spelled with a lower-case “c”, not a capital “C”
    2. You didn’t say what the “new file” size was after you took the K2PDF file through the calibre clean-up phase. Was there a reduction? I suppose you’re like my math teacher who said: “The demonstation is left up to the student.” Ha!

    Again, thanks for pointing me and my beloved Kindle in the right direction to make effective use of my PDF E-books!

  12. ssnjara

    @MeMechant just open terminal and type:
    cd ~/Downloads/ # or wherever you downloaded k2pdfopt
    sudo mv k2pdfopt /usr/bin/
    and than change permissions:
    sudo chmod +x /usr/bin/k2pdfopt

    to use it type in termnal:
    k2pdfopt filetoconvert.pdf

  13. boocat

    I’m still trying to figure how to improve some badly formatted free eBooks I got on my Kindle. But once something is in Kindle already, I can’t figure out how to get it into my Calibre account to put on a pretty cover, etc. I’m a computer dunce, so I guess it’s hopeless, but I keep limping along…

  14. Tom

    Unfortunately K2pdf doesn’t work on a Mac. Very interesting though as the text conversion is a problem I’ve experienced on my Kindle.


  15. Ken Esq

    mobipocket creator does this as well and it is very easy to use.

  16. Brad

    Briss is a utility that crops the text, while reducing the file size. Reading in Landscape mode provides about a 3 screens per page on my Kindle.

  17. Lady Fitzgerald

    Briss does not actually crop the margins, only the display on most viewers (Adobe Acrobat does the same thing). When viewed on my e-book reader (Jetbook Lite), the margins are still there (I had the same problem with the Astak Mentor). Fortunately my Jetbook Lite has various zoom levels and also has a feature that matches the width of the text to the width of the screen. Most scanned paper backs will be able to fit one page onto two screens when reading in landscape so margins aren’t an issue.

  18. MeMechant


    Your instructions are perfect thank you very much!

  19. lichen

    Ubuntu users, if understand latex, can try some tools included in texlive,
    -pdfcrop for cropping margins only.
    -write a latex file to use the pdfpages and forloop packages, compile with pdflatex to cut every large page into several parts.

  20. Frank

    Thanks for this tutorial

  21. Mohsen

    Very nice, thanks.

  22. willus

    I’m very skeptical of the conversion of the k2pdfopt output back through calibre, because k2pdfopt only saves bitmaps inside of its PDF output–no text or font information. So either calibre perfectly OCR’d the k2pdfopt bitmaps and figured out the fonts exactly (I doubt this, but I suppose it’s possible), or it somehow magically re-rendered the k2pdfopt bitmaps at higher resolution (which I also doubt). I think there is some cockpit error here. How did the size of the final calibre output compare to the k2pdfopt output file size?

    Also, the graininess of the k2pdfopt output bitmaps is entirely controllable w/customized settings. The default output is 800 x 600–the resolution of the kindle. There is no point in going to a higher resolution since it will be lost on the kindle. It only bloats the output file size.

  23. willus

    After playing around with calibre for a while, I am quite sure there is no benefit to running the k2pdfopt output file back through calibre to convert it to mobi. The supposed “text cleanup” that Jason sees is an artifact of the viewer he is using to display the file, which, based on Jason’s images, I’d guess is calibre’s own viewer. Calibre’s viewer resamples the 600×800 bitmap in the k2pdfopt output file down to 538×718, and it doesn’t do any antialiasing, so that’s what makes the text look grainy in Jason’s images. Viewing the same file in a better PDF reader like Sumatra (or on the Kindle itself) will look much better. When I ran k2pdfopt files back through calibre, all that happened was that they doubled in size and showed none of the “text cleanup” that Jason suggests.

  24. Slikdata

    Would like to concatenate multiple .PDF either before or after ePub conversion. Is that functionality in Calibre?

  25. willus

    @Slikdata — Try using jpdftweak to concatenate/merge multiple PDF files.

  26. Dr. Beverly Kurtin

    I CHEAT. The first thing I do is do a CTRL+A, CTRL+C

    Then I open up .txt file and paste the contents of the PDF file into it and load it via USB into my Kindle. Alternatively, I’ll convert it into a Winword file using Nuance’s PDF converter then send it to Amazon to be converted to a Kindle format.

    Alternatively, once I have the .docx file, I’ll copy/paste into a txt file.

    Also for copying the text in a web page, I just CTLR+A, open a .txt file then just upload directly into the Kindle.

  27. Allen

    Can’t do this on mac]

  28. Wendy

    I have a different kind of issue with an eReader that Calibre didn’t help with. After getting an epub file from my library to read, it came as a acsm file, which needed Adobe Digital Editions to “approve” it and allow the epub to be read. The issue is that I have a Samsung Galaxy 10.1 Tablet (running Honeycomb), and ADE will not download to it saying it is not meeting requirements. I’ve searched, and called Adobe/Samsung and no one is able to help, can you figure it out? The obvious of opening it on my PC (WIN-XP) then moving it to the tablet doesn’t work as it still looks for the ADE approval. Also tried every epub app available to the android. HELP. (thanks)

  29. willus

    @Allen– There is now an OSX (Intel CPU) version of k2pdfopt.

  30. StevenTorrey

    I don’t know if this is related but here goes. The Kindle my daughter owns does not read Hebrew. The book downloads but the Hebrew text ends up garbled. Maybe it was a bad day in cyberspace or something. The PDF format works fine giving a standardized product thanks to Adobe. The ebook is pretty much the same as the PDF format so nothing is gained and I would be hesitant to muck with something only to have the Hebrew or Greek lost. This would be especially true if my own PDF documents ended up garbled with Hebrew and Greek. You try typing in Hebrew or Greek– It’s a lot of work… And I’d hate for that work to go to waste…

  31. Allen

    To get documents on the Kindle into calibre, merely click on the Add and then navigate to the Kindle\Documents folder on the Kindle when it is plugged in to the USB and import them all or just the ones you want. Calibre will make a copy and put it on the hard drive so you don’t have to have the Kindle attached any longer. Also, one can edit TXT files on the Kindle directly by finding it in the Kindle\Documents folder and just double clicking on it to open it in your default text editor, do the editing and just save it again. It saves back to the original location, which is the Kindle.

  32. TeenMutantSupersoldier

    I use ABBYY PDF Transformer to convert pdf to html. I then use calibre to convert saved html to epub. options used in ABBYY depend on particular pdf. sometimes I convert to pdf to Doc and use openoffice to edit. in openoffice i use preview in browser option. I save that preview and convert to epub with calibre. that is the process for 6″ eink readers. for 10″ android tablet use i can just skip conversion and open saved html in opera mobile. Opera\opera mobile has a spectacular zoom feature that reformat text\images to fit screen on the fly [like but better than pdf reflow], I only wish i could use zoom in opera browser and “bake” the on the fly reformatting\reflow to a saved html, then take that file into calibre to create epub with new “baked” formating. i’m sleepy hopes this makes sense!

  33. James

    Thanks for the tutorial. I will work for me.

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