This IRS page claims that with the correct version of Adobe Reader, I should be able to fill in certain forms:
8.2.5.
Adobe's help file says this: "Noninteractive PDF forms can be printed and filled in by hand. Or, you can choose Tools > Typewriter > Typewriter and use the Typewriter tool to type information over the blank form fields and then print a copy of the completed form."
Silly help file. The "typewriter" function doesn't exist on my Tools menu.