There is a template PDF - a document representing a form to fill out. The fields to be filled are long rows of squares. One or another symbol fits into each square. You need to somehow fill in this form automatically. Are there any libraries (preferably .net) that allow to do this? That is, it is not just the insertion of text into a PDF document that is of interest, but the insertion of each character into a separate placeholder, which is somewhat more difficult.
I use for this purpose the iTextSharp library. It has all the necessary tools to fill out a template PDF document.
It seems to me that it is easier to create your own "alphabet" here. That is, a set of pictures, where there is an image of each character in this box. And "print" to the file with a set of these pictures. Well this option will help if further editing of this form is not required.