Can I change a file type using Property Calculator?

We import documents via Connection to external file source.
The files do not have a type / extention.
Instead the extention is found in an accompanying XML, so we use that to populate a Property.

Can we somehow bind the found property (ex. "PDF") to the Type?
Can we use the Property Calculator or any other tool to rename the file so the file's extention is added?

ex. d5aae826 becomes d5aae826.pdf