We created our own interface with column entities etc which can be created and edited by the end user with ckeditor. Then we combine the input and build html and put that into a mendix template that only uses this as xhtml and creates a pdf out of it. It’s a lot of work to create this interface (especially if you want to be able to add images etc) and the java library that Mendix uses to create the pdf is ancient and doesn’t support all css.
Another approach would be to try modules like this one or this one.
And Mendix 10 has improved (?) pdf generation, but I haven’t seen or tried it yet. Also it’s a bit early to use Mx 10 for production apps.