It seems that Adobe Freehand drawings were notoriously difficult to properly export to PDF format and quite often ome elements might have not been saved properly.
Some users circumvent this situation successfully by exporting to EPS format (PostScript) instead and then import this to some graphics editor like Fireworks or Photoshop and export that to PDF.
There is also a script available for download from Adobe that allows users to import old FreeHand drawings .fh, .fh8, .fh9 etc.) directly to Adobe Illustrator and save them as .ai drawings. Once done, you can easily print it as .pdf files.
This option however, seems to be working only for CS4/CS5 versions of Illustrator and does not work for the latest CC - Creative Cloud edition.