Unhelpful message that "Search has skipped __ files because ... these files are corrupt ..."

[AnAcrobatUser]

I did an advanced search in Adobe Acrobat XI Pro, looking for all instances of a particular text string in a folder tree. The tree has many thousands of files and the search found two instances, but also reported "Search has skipped 5 files because either these files are corrupt or you don't have permission to open them." That's troubling and the message is not helpful without stating the filespecs of the skipped files. There should not be any restricted files ​in this tree, so it's telling me I've got five corrupt files in there. I need to know what they are and see if I can find any reason for the corruption, and also go back in my backup archives to hopefully find and restore good copies of them. Is there a way to find out what files Acrobat skipped in that search?

[gkaiseril]

I would first try to open the files and see if there is an open password required. If not then there could be an issue with some feature of the file being converted into a PDF or the file may have become corrupt.

[AnAcrobatUser]

Yes, opening the files to test them is exactly what I want to do. The problem is that Acrobat is telling me that out of thousands of files in the folder tree, it found five that it can't open, but it didn't tell me which five. I need to know which files it had a problem with so I can test them.

[flexify]

Was there any resolution here?  This is a real pain.