Below I have inserted a table which shows how The PDF Info Dictionary tags and specific XMP tags are related and how they can be translated.
Thus, in your GUI, I assume you would create the PDF Info dictionary Fields (Title, Author, Subject, Keywords, Creator, Producer, creation date, modification date) for the user to fill-in and then the corresponding XMP tags (as shown in the above inline table) would be updated at the same time (as you said, enabling a check box would allow a user to also update XMP tags when they entered data in the info dictionary fields).
Other considerations:
1. how deletion of tags would be implemented (possibly overwriting with new entries)?
2. how duplication of tags would be handled/avoided (possibly by overwriting all tags present)
We look forward to learning about your progress regarding the above development. I also look forward to promoting and recommending your app when this above piece is complete.
Thank you kindly.
Regards,
Sam
See uploaded image: XMP_Metadata_with_Corresponding_PDF_Info_Dict_Metadata.jpg
XMP_Metadata_with_Corresponding_PDF_Info_Dict_Metadata.jpg