This is the ultimate solution. "Flattening" converts all text, fonts, and interactive layers into simple pixel images.
If you are tired of PDF errors, consider moving to a dedicated sheet music app that handles Khachaturian’s works natively: This is the ultimate solution
This is almost always malware. Legitimate publishers don’t do this. Immediate action: Delete the file. Scan your computer. Then go buy the $4 official copy from MusicNotes. This is the ultimate solution