Questions on pdfToolbox: Warning "Invalid Compact Font"

Question: What does the error message “Corrupt Font. Invalid Compact Font” that arises in Acrobat after creating a preflight or inventory report mean?

Answer: Some 3rd party plug-ins like PitStop Professional are incompatible with the method to create the preflight or inventory report. Currently this error message can only be avoided by deactivating the 3rd party plug-in.