Error as i try to Open file

[Angela njendu]

Could someone please let me know why I am getting this error message and what I need to do to be able to open files from my phone S9+
Thanks

 

[SpookDroid]

Which app are you using to open PDFs? Seems like whatever app that is is meant only for fillable forms (which prompts that error if your document is a 'plain' PDF). You need to change the app that handles PDFs. To change it, go to your Settings, Applications, Default Apps and look for whatever is handling PDFs now (and reset it or change it to the default PDF viewer or another suitable app).