Adobe Reader (PDFs) react in a similar fashion to the use of Grisoft's AVG Free Edition.
That is, if you miss 1 update this might be the vital one....to keep it properly updated!
If Adobe Reader is set auotmatically...to update itself, and you are using another program you consider too important to put aside until the update gets done that you 'cancelled' this update. (Because you found it 'annoying' to interrupt you at an important moment! OR, that your computer was switched 'OFF'....when this vital update is being delivered!)
And, now, you find yourself unable to read these PDFs, because of that.
AVG reacts in a similar manner. That it too stops functioning properly, if you happen to have missed a vital update.
That you have to give it permisson when it's pop-up window asking you to grant it ACCESS....to any update, appears. (Some people also find this an annoying 'aspect' of AVG, as it too interrupts you when you're doing something else you consider more important!)
The only way around this (that I know of) is, to simply UNINSTALL either program, then, once having downloaded the latest version available, to reinstall it.
Then, use the Update option(made AUTOMATIC by you or via the program itself!) either of these programs DO have contained 'within' their program......to make doubly certain that you do indeed have all the latest updates.
This actually applies to.....all programs that you may have in your computer.
Keep everything so well updated that (basically) you have all the latest updates........mere seconds AFTER they have been released.
Otherwise, you are just neglecting your computer...straight-out. (The 'human error' effect.......which is the biggest wrecker of all computers.)
If you have the habit of turning your PC 'OFF' when you are done with it, remember this little rule of mine......"When you switch it back 'ON', give it TIME to update itself, with those Programs that are set AUTOMATICALLY....to update! GO and have a cup of your favourite brew, tea or coffee, OR take a shower, make yourself breafast/lunch/whatever...while it is updating!"
No, you won't do that, either. (You're too busy! BUT, all the same, all the same you will sit there looking stupidly at the monitor while your computer is updating itself...being annoyed that it IS taking too long to do that that you will CANCEL the update....so that you can get to make use of the computer, in a hurry!)
Again, the good old reliable 'human error' factor strikes again!
And, you then write into a website like PCuser.......to say that you have another 'problem'...with your computer, yet again.
Your computer is ONLY as good as the time you are willing to invest in keeping it running properly.
(Nobody else can do it for you, since it is your computer!Not mine or anyone else's!)