I want to edit a pdf. How do I do it?

You can make minor edits in Acrobat and use a plug-in such as PitStop do do a bit more, but PDFs are not meant to be edited in the same way that the original document can be edited. What edits are you planning to make? If you can be somewhat specific, we might be able to determine how easy or difficult it would be.

If you were sent a PDF form, you can fill it in using the free Adobe Reader.