See [[https://tex.stackexchange.com/questions/365939/cannot-open-dde-link-to-problems-with-adobe-acrobat-pro-dc-2017-and-winedt]]

If you can't upgrade to the latest version of WinEdt, you can instead open a local copy of the file Adobe.edt from the Options menu -> Options Interface dialog -> Advanced Configuration -> PDF Macros -> Adobe Blues.

In this file, replace the line at the very end of it

{{{// Assign(!"Acro-DDE_Service",!"AcroviewR11");}}}
with the following

{{{Assign(!"Acro-DDE_Service",!"AcroviewA17");}}}
then save the file and restart WinEdt.

Addendum: Name of the DDE service for different versions of Adobe DC

{{{
Adobe Reader DC 2015: AcroviewR15
Acrobat DC Pro 2015: AcroviewA15
Adobe Reader DC 2017: AcroviewR17
Acrobat DC Pro 2017: AcroviewA17
Adobe Reader DC 2018: AcroviewR18
Acrobat DC Pro 2018: AcroviewA18
}}}

Unless Adobe changes its naming convention, for future versions it suffices to change the last two digits according to the year version.