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A
AlanS5100
Inspiring
November 30, 2016
Answered

Reader has corrupted my PDF

  • November 30, 2016
  • 3 replies
  • 3456 views

I always keep Reader up-to-date.

I used Reader to save my own version of someone else's 14.6MB PDF.  I then used Reader (and only Reader) to progressively add and save a few hundred words of comments to the file, which somehow inflated it to 17.6 MB (18,526,068 bytes).

19 days after my last save, Reader will not open my file.  Although I have a backup copy of the last save, this is also unopenable.  I do not have any archived copies prior to my last save.

When I open my PDF in Word, it is displayed as 18,526,068 "ӱ" characters in Courier New font.  It appears that Reader has overwritten every single byte of the PDF with the same data.

I can understand that a file can occasionally become corrupt, but why would Reader fill my entire file with garbage?

This topic has been closed for replies.
Correct answer AlanS5100

It's happened again, but I've now realised why!

I hadn't noticed that the document's security settings did not allow commenting, but the then-current Reader DC allowed me to add sticky note and highlight text comments to this secured document, as https://forums.adobe.com/message/3569813#3569813 suggests used to be the case with Reader 10.0.

Instead of giving me an error message when I attempted to save the file as my version with comments, Reader DC apparently deliberately corrupted it to preserve security. 

Version 2017.012.20098 has been tightened up so that it doesn't even allow sticky note and highlight text comments on a secured document.

3 replies

A
AlanS5100AuthorCorrect answer
Inspiring
September 29, 2017

It's happened again, but I've now realised why!

I hadn't noticed that the document's security settings did not allow commenting, but the then-current Reader DC allowed me to add sticky note and highlight text comments to this secured document, as https://forums.adobe.com/message/3569813#3569813 suggests used to be the case with Reader 10.0.

Instead of giving me an error message when I attempted to save the file as my version with comments, Reader DC apparently deliberately corrupted it to preserve security. 

Version 2017.012.20098 has been tightened up so that it doesn't even allow sticky note and highlight text comments on a secured document.

T
Test Screen Name
Legend
November 30, 2016

Well, Reader might have done it of course. But I don't recall a mention of it doing that. (Occasional corruption but remaining a valid PDF, certainly). The pattern is commonly used as part of "safely deleting" a file i.e. making sure the contents are not recoverable by disk tools. If you have any security software to do safe deletes, check into that. Clutching at straws I know but there isn't much to go on.

A
AlanS5100Author
Inspiring
November 30, 2016

Thank you, TSN.

Yes, if there were any content left, Word's Recover Text from Any File option could probably recover at least some of my comments, which is all I really need back.  Unfortunately, something has gutted my PDF and the last software that I know accessed it was Reader.

No, I've never owned any "safe delete" software, unless I have similar, as yet undetected malware! 

A
AlanS5100Author
Inspiring
November 30, 2016

Now that I know that Reader can behave like this, I can't really risk using it to comment PDFs in future.

T
Test Screen Name
Legend
November 30, 2016

It's also possible that SOMETHING ELSE broke the file after it was edited. You could look at the modification date, though some kinds of failure will leave that unchanged. Compare the dates on the backup too. And run a check for disk errors.

A
AlanS5100Author
Inspiring
November 30, 2016

I think I'd be more convinced that "something else" might have damaged this file if the corruption had not uniformly overwritten every single byte of the file.  I can't see how this has occurred without some software opening this file and overwriting it.  Defender in Windows 10 has not reported any malware after a full scan and I am not aware of any other corrupt files in my system.

File properties show that it was modified (that is, saved) 14 minutes after it was "created" and "accessed", all on 11th November.  This is consistent with what I recollect doing:  opening the file, editing comments for a few minutes and saving it.

Backup has identical contents, but some different dates:

  • Created:  28th September (which may be when I first saved my version of the file)
  • Modified:  Identical time on 11th November
  • Accessed:  13th November

The data drive is free of errors.

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