For a variety of reasons—frugality, environmentalism, laziness—I try to avoid printing documents whenever possible. That can get tricky when someone needs my signature. For example, I recently joined Macworld as a full-time staffer and was immediately sent a massive 80-plus page PDF welcome packet. Buried within those 80-plus pages were eight forms that I had to fill out and return to HR. That meant pulling individual pages out of a single PDF, then digitally filling them in.
You probably know how to combine PDF pages in Preview; separating pages is just as easy. To start, make sure the sidebar is showing (Command-Shift-D if not) and that it's displaying thumbnails of the pages in the document (if not, Command-Option-2). To pull a page out of the PDF, open it in Preview, click on the appropriate thumbnail in the sidebar, and drag it to your desktop. Preview will create a new file with just that page, giving it the same name as the original file with (dragged) as a suffix. If you Command-click to select multiple (even non-contiguous) pages from the sidebar and drag them all to the desktop, you'll create a single new PDF containing all of those pages.
Once I'd extracted the forms from the surrounding document, there were several ways I could add my signature to them; for example, we've written before about how to insert a scanned signature into a PDF. I prefer another way: I create a custom font in which one of the characters is actually my signature.
To create that font, I like the $7 iFontMaker iPad app from developer Elji Nishidal: It lets me use the iPad's touch screen to "write" letters in my handwriting, then combines those letters in a TTF font file. The trick I use to save my signature: Instead of drawing the caret character (^) in iFontMaker, I scrawl my John Hancock. Once I've installed my handwriting font on my Mac, I can type Shift-6 (the key combo for the caret) to insert that signature.
To do so in a PDF form, I use Smile's PDFpen or the free alternative FormulatePro. Both apps let me add text to an existing PDF and place it properly. More importantly, they let me select that text's font and font size. So I open the PDF form in PDFpen or FormulatePro, select my handwriting font, and type Shift-6: my signature is inserted. I then use the apps' text-placement tools to place and size it correctly. While I'm at it, I fill in other fields in the forms by "hand." Both apps let me save my completed PDF (still in PDF format), which I can then submit.