Ulrike Fischer's answer shows the previous similar questions are all out of date. The latest of them,
refers to AcroviewA17 and AcroviewR17 and these have already been replaced by versions numbered 18. Other advice in the answer to that question also has not worked for me but I think it not worth detailing the reasons since it is out of date.
I am using WinEdt 10 Build: 20170413 (v. 10.2) - 64-bit, and fully updated MiXTeK 2.9, with Acrobat Pro DC continuous release version 2018.009.20044. In fact the problem just appeared on another of my machines this morning, immediately after updating everything.
I had been using the options Start Viewer and Forward search. But just now PDFLaTeX and PDFTeXify have become unable to close the pdf for a file if it is open. And so they cannot do forward search.
If I left the pdf open from a previous run then, though nothing shows in the log file, a dialogue box opens saying
Cannot open DDE link to "C:\Program Files (x86)\Adobe\Acrobat
And a file called PDFCloseDoc.edt has this:
// DDE ============================================================== DDEOpen("%$('PDF-View')","%$('Acro-DDE_Service');","%$('Acro-DDE_Topic');"); IfOK(!"Relax;",!"DDEClose;JMP('Done');"); DDEExe('[AppHide()]');
// As of Acrobat 8 DocOpen must be done twice or else Adobe Crashes!
And even if no pdf is open, but I have the option set for forward search PDFTeXify creates a new pdf and opens to the first page but then when it would do the forward search it gives those same messages.
Is there an easy fix or should I try reinstalling something?
Describe essentially the same problem 4 and 5 years ago. Are those fixes still best or do they even work now?