I have been using an open SOURCE software called PDFSam recently, so I'm wondering if it happens to be something related to that.

Recently, SAVING PDFs from that software has left me with an unopenable document with properties as shown in the attachment.

The problem is, only some of the files in different folders with normal locations under Users have this error under the location with the question marks.

This actually kind of makes me nervous. Taking the file and placing in on a thumb DRIVE allows it to open...

Any ideas on what is wrong?

Thanks!I suspect the problem is that the full path and filename of the file is longer than 240 characters.

Short of it is that programs need to do some additional work to open files with longer paths so often programs simply cannot open such files.

if you copy it to a flash drive than you are probably plopping it into say E:\ so there aren't as many folders and the path is short enough that it falls below that limitation.

You COULD try renaming the file in question- it looks like the program saves them with very long filenames based on some TITLE information in the PDF so you could probably rename it to something more succinct.