Dataform documentation can be found at Dataform module. Essentially the Dataform allows you to create a Moodle activity where the user can add and view content entries. The Dataform PDF view type allows for exporting the activity content (one or more entries) as a downloadable pdf file.
If your requirement is feasible with the Dataform you would add a pdf view, enter the file content in the Entry template (HTML) editor, add some field patterns to capture entry author name, add pdf watermark and other pdf settings. Then when the user is granted permission to download he/she would go into the activity, add an entry and click export to download the content as a pdf file.
Here are some considerations. The content is entered as html and styling depends on css. The pdf library the Dataform uses (which is already included in standard Moodle) doesn't have particulary good support of css. So creating pdf content this way may not produce high quality result. Also, I see in your attached image that some files may be as large as 5 M. I'm not sure that the moodle form html editor would be able to work with that.
You may need a professional solution for creating pdf content if your content is rich or has to be high quality (e.g. Adobe Acrobat Pro). With the files created you can allow users to download them via a Dataform activity, such that the user gets access to the download link only after adding an entry which in turn records the user's access to the file. With a bit of further development we can add functionality that will set the metadata of the user's copy of the pdf file and add the user's name or some other info to the file's properties before downloading.
hth 
