Why is Acrobat Pro still not multithreaded?

I run into the same problem as you with running OCR on large insurance files which are pdfs of a wide range of formats from internal system documents, system notes, screenshots, emails, images, police reports, appraiser reports, etc.  Searchability was the stumbling block in one case which went through several hands before I OCR'd the files and located where a vehicle VIN was added to the policy of a 30-40 truck carrier that added and took away trucks frequently. Their insurance company said there was no coverage for vehicle because it was never added.  No one found the VIN on any endorsement. I put to rest a $500k problem because I let the program run for 45 minutes on my machine.

Now, to take care of the problem, we put OCR tasks on an old machine, limit everything else and let it OCR files while we work on other things.  Reminds me of a friend in the 1980s who loaded his dot matrix printer with paper and printed out an inventory report for his father's retail stores overnight. 

The problem that brought me here is that only pdfs hang when called from our case management software. These are pdfs from 500k to 5mb.  This problem is similar to the Creative Suite folks who complain that some functionality is slow or delayed when zooming in or performing other tasks.

 I discovered a possible interference earlier today which has nothing to do with Adobe. 

I have a spreasheet open at all times.  For a separate reason I went into the Advanced settings of Excel and scrolled through the menu.  I stumbled across "Formulas - Enable multi-threaded calculations"  Below it reads "Number of Calculation threads" .  What was selected by default was "Use all processors on this computer:  12."  Then in the General section was checked "Enable multi-threaded processing." 

I could be way off base on this.  I'm not a computer anything, but from working with Microsoft products a long time, my gut instinct is that Microsoft requires x,y & z before any other programs pull functionality away from its software. 

If Adobe needs to build a page and needs a processor to do so, then it needs one processor that Microsoft has allocated for its programs by default.  When I open two or three pdfs, Excel shares.  When I try to open more it's like Excel doesn't want to share the processors it was allocated and the Adobe page doesn't build until the allocation is resolved.  I even spoke with the owner and developer of the case management software with two of his devs via zoom and replicated the problem while he watched his program hang and could not explain what or why. 

In additions to all of the things in the linked Adobe thread, it might be that some other programs need to be limited to their own lanes, so to speak.  For what it's worth....