I need to take an existing pdf file and programmatically fill in a list of form fields with text and then save the pdf without ever displaying it to the user.

For instance, if the pdf file contains fields named "LastName", and "FirstName" I would like to set the value of "FirstName" to "Louis" and then save the file.

I've been searching for a long time and can't find any guidance on even where to start since the iOS documentation (and most of the questions on here) seem geared towards displaying or creating pdf content instead of modifying it. 

**EDIT:**  

My main question is: Is it possible to open a pdf stream (I know how to do this) and copy each existing pdf dictionary item into a new pdf? I have not been able to find a way to write the dictionary items to a pdf.