Certificate validation error

I recently had a curious problem while signing PDFs with a digital certificate using Assinador Livre, provided by TJRJ. It turns out Assinador Livre does not work on Windows 10, and because of that it throws an error when trying to sign.

The error is confusing: "Errors in the certification chain: 1) Certification chain cannot be built to its root". At first I thought it was the file path, but it was not.

The solution in this case was to sign the PDF another way. There are other tools that can perform the same task as Assinador Livre, such as SERPRO. Here is the procedure:

Open this site: https://www.serpro.gov.br/links-fixos-superiores/assinador-digital/assinador-serpro

Download the program, which at the time of writing is version 2.7.1 for Windows, Mac, and Linux, depending on your distribution.

If you want to learn how it works first, open the tutorial. If the link has changed, check the site above because the correct link may be there.