abracadabra-DocID is a plugin for Acrobat Reader
abracadabra-DocID adds a quick comparison tool that displays the « Permanent identifier » [ID] of PDF files.
abracadabra-DocID is free.
- The first string is a permanent identifier based on the contents of the file at the time it was originally created; it does not change when the file is incrementally updated.
- The second string is a changing identifier based on the file’s contents at the time it was last updated.
- Comparing the Permanent identifier [ID] of several PDF files quickly corroborates: exactly the same, not the same at all, or a variant.