I think, because Corp.
In Corp, they want someone to be in charge, and take reponsible when something mess up.
It is easy for IT to proposed to buy a solution, because the vendor take responsible for mess up, rather than use open-source and have to fix bug themselves.
There are also case where developer push malware into open-source.
This is another example, corp pay to use open source (https://tidelift.com/).
They are paying to have someone to cover them if something mess up, like a reliable mantainer.
So i think that why corp still pay for pdf solution, e-signing and stuff like that rather than implement from open source solution.
I think, because Corp. In Corp, they want someone to be in charge, and take reponsible when something mess up. It is easy for IT to proposed to buy a solution, because the vendor take responsible for mess up, rather than use open-source and have to fix bug themselves.
There are also case where developer push malware into open-source.
This is another example, corp pay to use open source (https://tidelift.com/). They are paying to have someone to cover them if something mess up, like a reliable mantainer.
So i think that why corp still pay for pdf solution, e-signing and stuff like that rather than implement from open source solution.