Hello.

Theoretically it's possible. Storage in Market app which is used to upload and store ZIP archives should be modified to accept PDF instead of ZIP. It can be done in DB -> 'sys_objects_storage' table. Search for object with 'bx_market_files' name and replace zip in 'ext_allow' field with pdf. Then you need to clear cache in Studio -> Dashboard and test. 

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Best Regards
Anton