Watermarks in PDF file downloads

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1 Initial Problem

Often course material as scripts or excercise sheets as well as their solutions are not intented to be distributed publicly for many possible reasons. In addition, the content of the files might change due to, e.g., correcting typos in previous versions. Therefore, it would be nice to have the possibility to automatically add a "watermark" text to PDF files in data collections. The watermark should be a text which can be customized by the uploader. It should also be possible to access fields like date, time, and user name of the downloader to create watermarks as "This file was downloaded at XXXXX by user XXXX".

2 Conceptual Summary

It should be possible to create watermark templates in editors similar like writing messages to course members. These watermark templates should be selectable everywhere where files can be uploaded. 

3 User Interface Modifications

3.1 List of Affected Views

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3.2 User Interface Details

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3.3 New User Interface Concepts

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4 Technical Information

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5 Contact

• Author of the Request: Philipp Scholz, University of Cologne, Institute for Nuclear Physics
• Maintainer: {Please add your name before applying for an initial workshop or a Jour Fixe meeting.}
• Implementation of the feature is done by: {The maintainer must add the name of the implementing developer.}

6 Funding

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• …

7 Discussion

Schmid, Fabian [fschmid] 2022-04-22: Hi, I stumbled across this feature request and wanted to comment briefly on what I think of it from a file services maintainer perspective:
I can understand the idea very well and find it very interesting as well. Unfortunately, I don't see how this could be implemented in a meaningful way at the moment: The main problem is that you would have to edit the PDF files on-the-fly. This would probably be technically possible, but not in all cases and probably not very reliable. There are many different PDF formats (e.g. PDF/A, PDF/X etc, see https://de.wikipedia.org/wiki/Portable_Document_Format#Normen_und_Standards). For some of these formats, no libraries are available that could be used under a suitable open source license. It should also be noted that the server load for each download of a PDF file could increase significantly compared to a normal download. This would not be a good option under full load. Last but not least, such a watermark would unfortunately not be very secure because it can be easily removed with very little effort.
For these reasons, I don't see any way to push this feature request further at the moment. Thank you for your understanding!

8 Implementation

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Test Cases

Test cases completed at {date} by {user}

• {Test case number linked to Testrail} : {test case title}

Approval

Approved at {date} by {user}.