How the creator of a PDF file sets up her document determines the extent to which you can use Acrobat Reader's commenting tools to mark the file with notes about its content.

Need to edit a PDF document but don’t want to pay for the more expensive Adobe editors? You can add text to and sign a PDF with just the free Reader program.

Just like how you add inked signatures on a hard-paper document, you can also add an electronic signature to your PDF document in the Edge browser.

Automatically convert a PDF file into a Booklet using these free software and online tools, to make a PDF document look like a book.

You can combine multiple PDF files into a single, easy-to-share document using simple software on your Mac computer or Windows PC. Here's how.

Fortunately, Apple has added the ability to electronically sign a PDF document using Preview, a program that comes preinstalled on every Mac running OS X Lion or later.