Based on the Github issue (#300) raised regarding the permalink, I have investigated the permalink settings further. Whilst the permalink could nominally be edited on the document screen, in reality the update did nothing. This has been fixed. Further, the permalink contained in the post is not valid. This change maintains the data for current posts. Also the validate structire process has been updated to enable correction for existing posts.

So, given that the post permalink is automatically corrected, the Cookbook facility for removing the year/month element from the permalink needs to be taken into account. This has been done by introducing a parameter into the permalink creation process.

The rewrite rules that work in version 3.4.0 for file called doc.pdf, this will be matched by both:
site_url/documents/doc.pdf
site_url/documents/yyyy/mm/doc.pdf

Thus if sites implement the new option, existing documents will still match.

This adds:
site_url/documents/yyyy/mm/

I added this since that is what the guid contained in many cases and seems a reasonable extension and is just a shorthand for
post_type=document&year=yy&month=mm