Here’s a little-known fact: There are applications that let you annotate and modify PDF files for free, with no watermarks. This way you can review a document and make your comments without wasting any paper in the process.

Update: Do not install Foxit. They are bundling search hijacking browser extensions that will ruin your day.

The application we’ll be using for this quick tutorial is Foxit Reader. This is an alternative PDF reader (alternative to Adobe Reader, that is). It’s fast, lightweight, and free. And most importantly for us, it lets you annotate documents.

For starters, download and install Foxit Reader. Then use it to open a PDF document you’d like to annotate. If installing Foxit Reader doesn’t make it the default application for opening PDF files on your system, you can right click the PDF and select Foxit Reader under Open With:

Once the file is open, click View > Toolbars > Commenting Tools.

The commenting toolbar lets you annotate the document in seven different ways:

You can underline words, highlight them, underline with squiggly lines (possibly to mark typos), cross text out,  add a “replace” mark for text you wish to change and add floating sticky notes.

You can also double-click any such marking (underline, squiggly line, etc.) to open up a note where you can type a longer explanation. This is optional, so if the other side would understand what you’re trying to communicate even without a verbose note, you might want to omit it.

By clicking the Options link on each note you can set its status, mark it with a checkmark and more. You can also change its color by clicking Open Properties.

The comments you make in the documents are readable with Adobe’s own Reader – the other side does not need to have Foxit Reader installed to read them (though they would need Foxit Reader or Adobe Reader Professional if they wish to reply).