PDFpen is a PDF editing and form-filling application for Mac OS X. PDFs are important to many people with disabilities because scanned documents are usually converted to PDF format. So for those who can’t handle physical paper, being able to edit or add to a PDF file is important. PDF files are also used frequently for online documents, especially those of a more “official” nature such as bills and bank statements.
PDFpen lets you replace text in original PDF files with editable text blocks. You can move, resize, copy and delete images, overlay text and images onto PDF files, insert and remove pages, reorder them using drag and drop, copy and paste rich text content, select and copy text across multiple columns and more.
Some of these things - copying and deleting sections from a page, and inserting/removing and reordering pages - can now be done by the Preview program in Leopard. The version of Preview included with Tiger did not allow for inserting/removing or reordering pages in a PDF.
There are a helpful screencast tutorials for PDFpen available too. I suggest anybody considering this program watches these to get a clearer idea of what it can do.