"Loading ads"

I am using "Acrobat for Samsung" on my Galaxy S9+ with Android.

Recently something changed so that I get the message "loading ads ..." if I open a local PDF file ( a PDF file on my phone). This takes several seconds, and evenually no ad appears.

I think I paid for this app when I bought my telephone, so it should not depend on advertisement income.

The PDF files on my telephone are from various source. Some of them I created myself. Typically, they are free of copyright (private copys are free, in my country).

How do I get rid of this irritating message? Is it perhaps malware?