13 Free Tools for Viewing and Editing PDFs

Adobe's Portable Document Format (PDF) has become something of a standard for sharing high quality digital documents. Unfortunately, many PDF readers only support a minimal set of tools for editing, annotating, or otherwise modifying PDF documents, and PDF publishing and editing suites, while powerful, can often cost an arm and a leg. Don't fret though, as there are a fair number of viewers that do more than just open PDF files, with loads of free tools to modify, split, merge, encrypt, or digitally sign these electronic documents.