There is some link between the two but not in the sense you are figuring out. The ICDD PDF database is quite large right now and contains most of the ICSD entries (at least those that are not duplicate), suitably corrected when errors or inconsistencies (frequent) are found.
In the PDF2 database you find just the ICSD reference number related to the ICDD card. In the PDF4+ database you don't just find the ICSD reference (if available), but you also find thoroughly checked atomic coordinates for a large part of the compounds (and this is something few people have yet to realize). So if you have the ICDD database you can already find the information with a simple search.
There is some link between the two but not in the sense you are figuring out. The ICDD PDF database is quite large right now and contains most of the ICSD entries (at least those that are not duplicate), suitably corrected when errors or inconsistencies (frequent) are found.
In the PDF2 database you find just the ICSD reference number related to the ICDD card. In the PDF4+ database you don't just find the ICSD reference (if available), but you also find thoroughly checked atomic coordinates for a large part of the compounds (and this is something few people have yet to realize). So if you have the ICDD database you can already find the information with a simple search.