If you know JSON, you probably are somehow my target audience.

Imagine you could take your normal Word document and just put in some placeholders. Then send some JSON and this Word document (as a template) to my service. You would get a PDF in return.

Instead of MS-Word documents I use OpenOffice documents as templates.

OpenOffice is a word processor like MS-Word. Also a nice user interface etc. it is just build with different goals in mind.