I have a similar issue. I have Adobe Acrobat Professional 2017. As you, it takes ages to open/close files, and occasionally hangs. A guarantee 'hang', however, is if I right-click on a PDF file because I want to open it in Acrobat as opposed to the reader (which I've switched to the default because Acrobat seems to insist on trying to make the PDF editable even when I don't want it to, and I haven't worked out how to switch it off yet).
I'm using Windows 10 with all the latest updates installed. I do know there is/was an issue with creating PDFs from FrameMaker after a recent Windows update, but I was still able to work with PDFs themselves. This is going to be a real show-stopper soon...
Is there any way to get support involved? I want to open a support ticket, but it doesn't seem available as an option.
As you mentioned all three users are from the same organization.
there is a possibility they all are using a third party app which is causing Acrobat to crash.
You can try Clean boot once https://support.microsoft.com/en-in/help/929135/how-to-perform-a-clean-boot-in-windows
Clean boot doesn't result in any kind of difference in the software. Is it possible that it has to do with reaching out to the network? Are there certain ports that should be opened when using this product? Anything specific that needs to be tweaked in regard to firewall settings?
I have solved my "hang" with Acrobat. I had to disable a shell extension. I couldn't tell you which one was the culprit, as I disabled any I don't use.
I do now I disabled the Dropbox one, a couple to do with my graphics card (I don't play games, so don't need to be able to do anything clever there) and one called "Play to" which has something to do with streaming. There were others... if I've never used them, I've disabled them. To do it, I downloaded the utility ShellExView from http://www.nirsoft.net (there's also one called ShellMenuView). Read the instructions, as they recommend hiding the Windows extensions so you don't stop something critical from working.
It's safer than editing the registry, although I did find sometimes something seemed to have solved my problem till I rebooted (hence the reason I disabled everything I don't use rather than stepping through one at a time).
Hope this helps someone...
Disabling shell extensions sounds promising, but I also came across this forum post which mentions required ports and endpoints (URLs) for different Adobe products:
It turns out a few of them are categorized as file share sites and can wreak havoc with certain firewall setups. Our network admin pulled the relevant ones, edited the firewall and now...we wait.
Allowing the listed ports/URLs for Adobe DC Pro functions seems to have done the trick. It's been days since the change was made and the random Apphang and 'Not Responding' messages are gone.