FillPDF syntax for multiple webforms
After many back and forths, I figured out the syntax for using multiple webforms (and this can be applied to NIDs).  The syntax would be:

http://yourwebsite.dd:8083//fillpdf?fid=61&amp;webforms[0][nid]=33&amp;webforms[1][nid]=19  

You can increment the webform number and continue to add NIDs.  I am pretty sure that this syntax works with SIDs as well, but I have no need for anything other than the most current submission at this time.

Additionally, note that as of the writing of this... this does NOT work the production version (7.x-1.10) of FillPDF but ONLY with the development version (7.x-1.x-dev).