IF you are using FIleMaker 12, specify external storage and do not use the "store a reference" option to insert the files. The files will be stored externally, much like "by reference" but now your remote clients should be able to see the PDF's.
If you are not using FIleMaker, a third party tool: SuperContainer, may be of use to you for this.
A third option is to use VPN or remote desktop access to open the database. Since this opens the database as though from inside the network, you should be able to see the PDF's that way.