Print to File is the bottom option on the far right-hand side. To print to file, you put a checkmark in the box, and then click the Print button. (Remember to remove the checkmark afterwards or you will wonder why PAF no longer uses your printer.)
PAF Companion can also be used to create a PDF version of an Ahnentafel book. If you click on Print, it will create an RTF version of the Ahnentafel book. There is no need to search for the Print-to-file option, as this is automatic. As mentioned before, save the file as a standard Word DOC file for better results when sharing it with others.
And better yet, if you have a PDF writer, create a PDF version. Everyone will be able to read it (but almost no one will be able to change it.)