PDFpen for iPad and Mac on sale for 50% off
PDFpen by Smile Software lets you easily fill in, annotate, and otherwise work wonders with PDF files, and what's even better - there are versions for both the iPad and the Mac. I've used them for everything from marking up ebooks for editing on my iPad, to filling out government forms on my Mac, and they've worked terrifically well each and every time.
They're both well worth the full price, but you can get either one or both right now for 50% off. If you frequently find yourself dealing with PDF, save yourself some Adobe-pain and check out PDFpen, and then let me know what you think!