Can we restrict a user to not upload certain file types in a document of record?

Yes, we can restrict users to not uploading a certain file format.
Setup and Maintenance
Manage Attachment File Formats
This task allows you to configure the file formats that you want to restrict from being attached. The feature works as an "exclusion".

I hope this blog post was helpful for you. If you have any questions or feedback, please leave a comment below.

Global Human Resource
Posted by : Mohammad