Why are text elements missing when my client uploads a PDF to an eDocBuilder image field?

You can setup eDocBuilder templates to use image fields that will accept PDF files as part of the customization.
But because PDF files can be created and manipulated so many ways, there are quite a few limitations that will determine whether they can be used successfully as part of an eDocBuilder template during customization.
Typically, PDF files that are interactive (not in the eDocBuilder sense of "interactive"), such as forms that allow you to fill out a PDF then save it with the added info, may cause problems.
Also PDF files where edits have been made within Acrobat may also run into issues, such as elements dropping out. Examples of changes include adding text, cropping the PDF, resizing page boxes, adding shape elements, adding comments and markup.
If you want to add such elements to a PDF file that can be used within a template's image field during customization, we recommend that such changes be made inside a true editor like Illustrator or InDesign. Add the elements in (such as text, shapes, or resizing the file's page boxes), export to a PDF (just a standard, non-interactive pdf), then use the updated PDF file in the image field during customization. Otherwise, the file is not considered "print ready", and eDocBuilder will ignore any elements added in Acrobat such as comment text boxes, and other markup.
Another thing to check is whether the file you're trying to use has layers that are set to "never print".
Within Acrobat, on the left side, open the layers pain. Right click any of the layers, and choose "Properties". The drop down, "Print", make sure that all layers you want to show up are set to "Prints When Visible"
There could be many other reasons elements are dropping off, including some of them being set to overprint when the color is white (0,0,0,0), and other preflight issues. Many of these can be caught and corrected by our prepress automation product, tFLOW. For more information on tFLOW, please reach out to your salesperson, or open a ticket with us.