PDF signing is the bane of my existence, luckily I can get by with a cloud solution but it's nowhere near how easy I wish it would be. Sadly I'm still forced to use a Windows VM or dual-boot because the tax authority in my country requires a root/digital certificate for login to their web system, at least for incorporated entities.

Would this procedure work with the certificates you need to use?

https://enterpriseadmins.org/blog/lab-infrastructure/install...