Two approaches ... sort of summarizing what's been said already:

1. Put text into the ABC source.
This works well if the text is fairly simple and the layout requirements aren't very fancy. The "ABC Plus" standard (as implemented by abcm2ps and any software that uses it as a back end like ABC Navigator) has quite a lot of directives available for controlling text appearance and layout.
%%begintext and %%endtext are more useful than W: if the text is non-trivial.

2. Convert the PDF into a graphic and import into a Word processor Document.
This is the best way when the text and layout dominate. For Mary's song book, we converted the PDFs (actually .PS, but converting between them is easy) of the tunes to 300dpi .PNG graphics files, cropped them and imported into an Open Office word processor document as pictures, along with other illustrations.

Note that the OO word processor can export direct to PDF, so if that's the format you want to end up with it's a particularly handy choice of WP. (and it's free!)

As John suggests, editing PDF files is not practical. Regard PDF as a final production format, not for work in progress.

Anahata