Each photo is assigned a unique ID by Fulcrum to ensure that there are no issues with photos sharing the same ID. When you go to export the photos out of the main exporter, you will notice that the photo's file name is this unique ID. This is done for the same reason, to ensure that there are no conflicts with multiple files sharing the same file name.
For PDF reports, the record ID is used by the web app when generating a PDF report for the same reasons above.
Due to the potential for file name conflicts, Fulcrum does not allow users to set their own file names for photos or PDF files within Fulcrum.
However, what you can do is rename the files once you have exported them out of Fulcrum using a file renaming program. These programs can leverage the exported CSV file and rename the files based on the column(s) in the data file that the user sets for the program to use. The program will locate the row where the ID of the file is located and then reference the cell in the column(s) in that row that the user has set the program to use for the new file name and then set the file name accordingly.
Here are a few examples of programs that can do this. These are just examples that either we have found or users have shared with us, we do not officially endorse or provide support for these programs.
We also have a help article on using a script to rename your PDF files.