SPDF files are regular portable document format files that have been "sealed" by a program called Oracle SealedMedia Sealer. This means that these files can only be opened by computer users that you specify. If you want to convert an SPDF file back into a regular PDF file that anyone can open, you need to use a program called Oracle SealedMedia Unsealer. You can install these two utilities on your computer at the same time.
Double-click your SPDF file to open it up in Oracle SealedMedia Unsealer.
Click the "Unseal" button in the Oracle SealedMedia Unsealer toolbar.
Select a name and save location for your soon-to-be-created regular PDF file.
Click "Unseal" to remove the seal on your SPDF file, which will convert it back to a regular PDF file.