Place a tag in the PDF

Hi all;

TL;DR - I need to place a tag that I will later substitute with data in the PDF. If possible I want to have a short set of text that is visible and a longer set of text that is the full tag and that can be viewed as a tool tip.

Full use case - I am trying to fit our docgen solution to use a PDF as a template for a document. This is for the case of say a tax document where the form is provided as a PDF and parts of it need to be populated with data. So the PDF itself is not adjusted, it's just enter the data in the appropriate spots in the document. Where the data is entered, we want it exactly lined up, not too high or too low. The tag we place there can be a very long select statement (or several). We don't want that rendering all over the document, but rather would like something like "[FirstName]" as the visible part. But there are times the user does need to see the entire select so having it all show as a tooltip to that short text would be great.

How should I do this? Both how to place it, and how to know I'm on it to edit or delete an existing tag.

thanks - dave