What are web open source constructors for generating documents?

Question

open source

Good afternoon!
Tell me, are there any web open source constructors for generating open source documents? Maybe someone has come across something similar:

The contractor claims that this is his own development - it's hard to believe, since the company is less than 5 years old (and in addition to this module, they also have a bunch of BPM things and so on).

Answer 1

https://solutionsreview.com/business-process-manag...
further on its own,
but in general there is no lick, in the same Alfresk, external offices are used