Starting with the 7/31/17 cut, whenever the AcroPDFImpl DLL_PROCESS_DETACH event fires, the module puts the thread to sleep and causes 2-3 second hangs in the process that loaded it. This can happen in all sorts of places for an application that embeds PDF content.
I ran some PE file analysis and turned up a new string in the most recent version (compiled 11/4/17) and found an interesting string (bDisallowDLLUnload).
I recognized this as a registry value because of previous experience with bProtectedMode causing similar issues when enabled.
I tested the following and found that it resolved our issue. I assume it causes Adobe.dll to leak a handle when it loads AcroPDFImpl.dll so that we just avoid ever hitting its DLL_PROCESS_DETACH event.
My question is why is Adobe code calling the sleep even when security registry settings (like bProtectedMode) is disabled. It seems like this registry key was added in response to the 7/31/17 change. Why not fix the issue instead of providing a completely undocumented registry setting instead?
In any case, hopefully other folks affected by this will see this post and try the bDisallowDLLUnload value.
Flash forward to November 18, 2020 -- I've been having lots of issues with Adobe Acrobat DC crashing for end users - Specifically the browser plugin - after loading 4 or more PDFs in a workflow chain the browser / application would crash out trying to load the next one - this registry key saved the day. bDisallowDLLUnload - DWORD - 1