This worked for me with another federal document (no comment on whether
the IRS will accept it). I saved the PDF form as an EPS (encapsulated
post script) file. Opened it back up in Acrobat and all editing was
available. Of course, the original form fields are gone as the entire
document is treated as text, but I was able to fill the form fields
before converting to EPS. After editing, then re-save as a PDF.