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I have a few questions. My website allows people to create custom 'puzzle' and education (i.e. "math") worksheets -  enter your 'school spelling list' - I can make a crossword or many other puzzles (PDF form) from it. I recently realized that I was being penalized for the backlink I placed in each one. I placed in each PDF ("Created with mydomain.com Crossword maker") - I was linking the "crossword maker" back to my site. BAD!  I am now aware of this.  I have recently disavowed several hundred backlinks where people have posted those PDF's online - and have started to see a big recovery in ranking and traffic. My questions about my citation: "Created with mydomain.com Crossword maker":
1. Moving forward, can I leave the same citation on each PDF - but just link 'mydomain.com' back to my domain (not the keywords, just the domain)
2. If not, can I just leave the unlinked text on the PDF: i.e. "Created with mydomain.com Crossword maker" -no embeded links at all.
3. Is it OK to assert that they must leave the "citation" (linked/unlinked?) to post them on their website as a part of my terms of use? If not, is there an acceptable way to get credit for giving away free custom content - other than asking for an 'optional' link back? I have thousands more of these that I would need to end up disavowing so knowing exactly what is permissible is extremely important to me moving forward. I have watched this whiteboard Friday: https://moz.com/blog/backlinks-maximize-benefits-avoid-problems-whiteboard-friday (I am looking for clarification on what I can put in the original content I essentially syndicate - the content is different on each and every PDF, except for the citation). Thank you so much for your time and help!