Hey there!
Can you please make sure all the old assets from 7.0.1 were deleted before upgrading. This includes clearing your cache, deleting the lib folder, etc.
We recommend naming the folder you store the library in after the version. So instead of Content/Imports/PDFExpress/lib you would do Content/Imports/PDFExpress/7.1.0/lib. This ensures the cache is reset after each upgrade.
Thanks,
Logan