PDFs are wonderful for forms, manuals, brochures, spec sheets, and the like. Where I work, we construct and output all of our job submittals and manuals electronically now. This requires creating and organizing various PDF documents, bookmarking them, and presenting them as a single, easy to use document.
The PDF has become the de facto standard document of the digital age, and is now just a normal part of life on the Internet. Our Deals site has a current special on PDF Expert 2.2 from Readdle. This is one of the best and easiest to use pieces of PDF editing and annotation software on the Mac.