I am studying this question.
I think in this post the best way is limit to the fields windows give : summary properties, word file properties, photo exif properties. Really I think is enough with the general properties.
Paperport seems to use these general fields.
What I noticed is that not all metadata programs show these, what I call, most basic of all fields (or tags in metadata speak.)
I did test ExifToolGUI with a Word doc and it does show FileName, Author, Keywords, Comments and Category. Filename is always there anyway but I added data to the Author, Keywords, Comments and Category fields/tags using the context-menu > Properties > Summary tab. After I refreshed the file in ExifToolGUI all were displayed.
But PDF's are a different story. For it to display the information it has to be entered into the fields/tags using a PDF program. For example, I use PDF-XChange viewer. I opened my test PDF, selected Properties and added info to Author, Subject, Keywords, Description Writer and Copyright Notice. (This is more than you are looking for but tested all of them) After I saved the file and refreshed ExifToolGUI all were shown.
Trying to do the same with the context menu > Properties > Summary tab... I could enter info in these fields but none if it was displayed after going back to ExifToolGUI and refreshing.
By the way, you may have already noticed, ExifToolGUI is a GUI that has been written to work with ExifTool. ExifTool is a command line program only.
Anyway, hope some of this helps you or others that may read it and been through similar frustrations.
I'm still going to try Imatch in a day or two to see if it handles anything differently.