IPad, Acrobat Reader, Content (text and pictures) no longer showing, just blank pages

Question

Hi,
I have a user who successfully opened a .pdf attachment from outlook mail and then opened it in Acrobat Reader on the iPad and then edited it and moved it to a created folder.
Everything was working fine and the user highlighted text in the .pdf document too.
What then happened is when the user subsequently opened the file, the highlights were shown but not the content (text and pictures).
I checked they had the latest version via the apps store updates and noted there had recently been an update which had been applied.
I did check also in the diagnostics to see if there were any acrobat files, but there were none, I also turned on 'send diagnostics' in case this this will help in the future.
I rebooted the iPad by pressing and holding the power and home buttons until the apple logo appeared.
Checked again to see if I could view the .pdf  content (it's around 8.5 MB file with 32 pages), still nothing showing apart from the yellow highlights that the user had done.
From within Acrobat Reader on the iPad I chose to open the file in iBooks to see if I could read it there.  I could successfully open the file in iBooks and the front page thumbnail was showing (I did note that in Acrobat reader the thumbnail was white).
I found the email with attachment and opened it again in Acrobat Reader and it opens correctly, suggesting somehow the previous copy had become damaged?  I have now saved this good copy over the top of the existing bad copy and all is OK except that the user has lost the highlights previously made.
Can you give me some idea of how this file has become broken in Acrobat Reader on the iPad and how I can avoid it happening again.
Many Thanks.

Answer 1

Thanks for replying.
This is the first time it has happened, the user has several folders containing files (on their iPad), (some .pdf's with additional highlights) these files are typically company agm board packs so contain pages of text and photo's too.
I put it down the fact that when I checked the app store for updates there had recently been an update and the user had not rebooted their iPad for some time, hence some of the underlying adobe reader files were perhaps between versions.
I don't know how you handle files when performing an update, do you close the app, flush files from memory and do a clean update?
I can confirm that the .pdf file had not been sent  as an email attachment after having added the highlights.
Because the acrobat document contains so many pictures (32 pages and 8.5MB) when scrolling through it takes several seconds for some pages to appear, and others with text and pictures quite a while for the text to become sharp, I presume this is because the Acrobat Reader cannot open the 8.5MB file in one go and has to keep swapping it out of memory.  Having reached the end if I scroll back to the beginning it takes 10's of seconds before the first page re-appears, otherwise it's just a white page.  Interestingly in iBooks the pages appear almost immediately when viewing.
The iPad in question is model MD368B/A, 64GB, Software Version 7.1.1 (11D201) and has 28GB Memory available.  Usage tells me Adobe Reader is taking 328MB and is version 11.3.1
I have just finally browsed back to recent documents, opened 2 or 3 other documents and then this one again (from recent) and it is now broken, just shows white pages (and on the thumbnail too) with my test highlights. so I can now apparently reproduce it.
Hope this all helps you re-produce
Regards,