Since you are new "export" is a specific procedure and the term refers basically to files intended for data transmission.
RTF would not qualify as "export" as such because of accompanying formatting and such of tables.
Since you are generating RTF (or any other ODS destination) you have to close the destination, otherwise SAS has the file still in use and would be considered locked.
Very brief example:
ods rtf file="somepath\somefile.rtf";
Proc print data=sashelp.class;
run;
ods rtf close;
You can have many different procedures that generate output inside one Ods destination "sandwich" but you need to close each destination. The "sandwich" is a very informal term relating to the pair of "Ods <destination> ; Ods <destination> close; The first is the top slice of the sandwich and the close is the bottom slice.