Re: A week after placing several small PFDs of my Nexus, there is substantial lag time opening the P
First, if you haven't already tried this, restart your N7.
Next, try a different PDF reader. If you're using the stock document reader, install Adobe Acrobat Reader instead. If you're already using Acrobat, try uninstalling then reinstalling it. Or try Kingsoft Office, which has a PDF reader as part of its office suite. However, its not as fast as Acrobat. Both of these apps are free. Other alternatives, some of which are paid apps, are also available, of course.
I suppose you could also try clearing the cache of your N7, but generally the cache allows you to access files faster. Still, it's worth a try and won't hurt anything.