Can you please tell us when you get these prompts.
Does it happen when you click hyperlinks to PDF's on internet pages?
If so, and after confirmation, do the files open in a separate window or in the browser window?
Are you using Internet Explorer 11 / Chrome / other browser ...
Does it happen in other circumstances?
In PDF-XChange Editor, via Edit > Preferences > File Associations, you have several options to set if this application may be the default for opening PDF's, if you like to view PDF's "in" the browser, and so on ...
Is there any relation with one of your previous posts ...viewtopic.php?f=65&t=27456