PAF4 may be looking for a GEDCOM that shows the gedcom version as 5.5. RM4 only exports as version 5.5.1 and UTF-8 only. Open the GEDCOM in a word processor (notepad is best) and change 2 VERS 5.5.1 to 2 VERS 5.5. This is about the 16th line down in the gedcom. Save the GEDCOM as Save as with a .ged extention as part of the file name, i.e. Mygedcom.ged. Then import the changed GEDCOM into PAF4.
RM4 makes use of GEDCOM extension that other programs may not recognize, such as Unicode [UTF-8] or User Individual Identification numbers [UID] used in Share merge. If going to programs other than RM4, try unchecking the GEDCOM Export box "Extra details (RM specific)" to tell RM not to incllude the extra RM4 details.