Stop Edge from taking control of PDF's permanently!!!

With all due respect, that is just spin.

I have the same problem, in that I set Adobe and Chrome as defaults for pdf and htm files - through Control Panel - and, sometimes within hours, they revert to Edge.  I have just had them stay correct for about two weeks, which is some sort of record.  And, no, I haven't reinstalled Adobe or Chrome or made any other changes, too busy, and far too busy to have to constantly reset Microsoft's dictatorial policies.

@Lester - is this a possibility? If you open Windows Settings > Apps > Default apps > Choose default applications by file type and click on the current entry for .pdf, is there any other option than Adobe Acrobat DC?

Just to be crystal-clear about my (previous) situation:

1. In "Windows Settings » Apps » Default apps » Choose default applications by file type" it always showed "Foxit Reader" (respective "Adobe Reader" or "sumatra pdf" when I tried those) after I had declared this application as default, using either this window or any of the other possibilities (e.g. "random pdf file » context menu » Open With » Always use..." or manually changing it in the registry)
2. But after minutes to days it went back to Edge.
3. Absolutely no signs of ACDSee interfering in "Windows Settings » Apps » Default apps » Choose default applications by file type". Also nothing in in Administrative » Event Viewer.

So, in my case, the playing around with "Windows Settings » Apps » Default apps » Choose default applications by file type" was not helpful (because Windows itself was not the cause of the issue).

The vector ACDSee used to (re-)set itself as default pdf reader is the following (screenshot from Process Monitor):

It looks to me as if a safety feature in Windows detects this change as unauthorized and therefore resets to Edge moments later.

Hi Greg

Thanks for your reply.  I didn't have this problem until the other day when Adobe made me upgrade from my old, and better, Adobe X to the online version.  I have done this on my laptop and not had the problem, only on my desktop.

I have tried a dozen times to set Adobe as the default through the pathway that you suggest.  But once I have had to do this a number of times within one session I figure that there must be a better way.

I will start by uninstalling Adobe and see what happens next after reinstallation.

I unchecked the PDF file association in ACDSee and that fixed it.

Thank you very much for posting this. I must admit that the possibility of some program other than Adobe asserting itself as the default in defiance of User Choice hadn't occurred to me.

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@Lester - is this a possibility? If you open Windows Settings > Apps > Default apps > Choose default applications by file type and click on the current entry for .pdf, is there any other option than Adobe Acrobat DC?

Thanks for the idea.  I did this but it has not solved the problem.

I am very frustrated with Microsoft Edge continuously hijacking PDFs.

Just to set the record straight, Edge isn't hijacking anything. Windows 10 has a number of default apps for a few things so the user is never left high and dry. Since XP days, there has been a default browser, a default media player, a default mail client (except for in Windows 7, and that caused untold angst for hordes of users), and later, after Adobe released the PDF standard to open-source, a default PDF reader. Following all the expensive hullabaloo about browser choice, the concept of user choice was introduced. 

When a user changes a default app - using the Default apps settings page, or by selecting Always use this app ... in a file-open dialogue - the association is registered in key called UserChoice. Now, if an app comes along and tries to register itself as the default for a file type, Windows will reject this attempt to interfere with the inviolate User Choice and restore the Windows default. For PDF files, that is Edge. This mechanism also prevents malicious, accidentally-downloaded apps from making changes like this.

Older versions of Adobe Acrobat regularly try to reassert the program as the PDF default, causing the change you observe. This was corrected in later versions (released 2018 onwards), so the solution is to upgrade Acrobat to the latest version.