Import PDF

I would recommend opening the PDF in Adobe Acrobat and checking the Properties tab to see what application was used to generate the PDF. It would be best to make any edits to a copy of the original file in its host application.

Artwork contained inside PDF files can be a horrible mess. The mess tends to be worse when the PDF is generated by an application not made by Adobe. Astute Graphics' Vector First Aid plugin can be a big time saver for fixing a lot of problems with imported PDF artwork, but it will not fix everything. From time to time I get stuck having to repair/re-build PDF-based artwork provided by customers because they can't get or can't find the original artwork. Repairing logos or other graphical elements from a PDF is one thing. I'd really hate to have to repair a complex PDF map.

You should be editing the map in the original application you created that in. PDF is not meant to be your master format.

If a client sent you a PDF and is asking for edits, they should expect to be charged hourly or that is not even possible. 

Maps even done in the .ai format can get quite complex. For cartography, I often use symbols for common objects like trees which helps speed up the file. Working in outline mode can help depending on the art. I always do a aves as to .ai. Sometimes you can do a group select, copy& paste into a new file, do your edits and paste it back into original. Would be helpful to see your art in preview and outline mode.  Seeing your links palette would be informational, as you may have many embedded items. You also can change your document raster effects settings to 72dpi to make the edits. I have plenty of more ideas as have been fixing issues like this on a regular basis for over 30 years, but need to see the file.

You might want to post a screenshot and give us a simple example of one thing you want to do. We may be able to share a tip then if we focus in detail on one thing.

You also might be able to open in Acrobat and edit the PDF there, or use edit in Illustraro on one object. Is very dependent on how extensive the updates you have. Maybe you need to update some type or move one item, or maybe you have extensive changes???

Those masks typically in a PDF are clipping masks and yes, they can be released. You will get a lot of unnecessary invisible paths (the former masks) that you might want to delete. You might also make things visible that were hidden by those masks.

And then also you might just not want to release the structure of the file. You can use the isolation mode to edit the paths in your map. Just double click the element you want to edit and then edit it.

Releasing a mask: Object > Clipping mask > Release.