PDF file type not recognized

It's PDF-A, I think.

Where is it not recognized?

• When you double click it?
• When you download it? If so in which browser?
• By your virus scanner?
• In your OCR software?
• In Adobe Acrobat?
• ...

all of the above except the OCR scanner is not relevant; the virus scanner has no problem with it & I believe Adobe Reader is what you meant & it won't read it. By the way, the file name is FIL#####.CHK

I see. So this does not affect all PDF files, but it affects one certain file.

The file extension .CHK is used for several purposes. One of them is to store file fragments, that had been found during a disc check. CHK files are no PDF files. Maybe what a special CHK file contains, once was part of a PDF, but it can also be everything else.

You can try opening the file with a text editor. What are the first 10, 15 signs, which you see then? If you are lucky, these signs actually come from the beginning of a file. If that is the case, then I will be able to tell you, which file type that actually was.

Why do you think that this one file would be important? Do you miss something?

I am a volunteer at a non-profit charity. Both the real filename must match an *.tif file & the contents must match. It purportedly was converted from the TIF by a latest-1 authorized version of Acrobat. I have 1000's of this files to verify.

So you have a .tif file. That is an image file format. (And it is one of the formats, which can be used to convert a PDF into it: Using Adobe Acrobat, you can convert a PDF into a tif file.)

And what else do you have? A second file, which must be identical to the tif? So a second tif? A copy?

walkerpbus said:

It's PDF-A, I think.

Maybe you just need to add a default program association for the "PDF-A" file extensions ?
A search for pdf vs pdf a finds many articles that might help, such as this:
PDF/A - Wikipedia, the free encyclopedia

I've got a more complicated problem, I think: File Explorer (FE) sees the file as FIL#####.CHK my task is to match the PDF's real file name to prove that we've converted a *.tif file to the pdf. When the FE creates the FIL#####.CHK, the file name can no longer be matched/compared to the *.tif file. :-((

I do not understand what the actual problem is.

You have very many files and for each, the situation is the following:

You have a TIF file.
And you have a PDF file, which has been created out of the TIF.

Now you say that Windows Explorer sees one file as a CHK file. Windows Explorer will only show files, which actually are there. So is the CHK file in fact the third file then - apart from the PDF and the TIF? Or do you in fact only have two files and one of the two files is named incorrectly? If so, which one is named incorrectly?

Please answer my questions above!

And what is it now that you want to verify? Is it the mere existance of a file (without checking the content) or is it that you believe that the file contents could be wrong and that you want to check them (which will be way more difficult)?

Only 2 files, the PDF shows up fine in Win 7, but appears as a CHK in Win 10. Yes to your final question. We converted a lot of TIF to PDF for a data base of archives. We want the final result to be PDF