Adobe Reader supports users to digitally sign documents,
but you have to apply an Adobe trusted PDF Signing Certificate from a CA first.
The only difference to buying MeSign PDF Signing Certificate from other CAs is the price!
Selling PDF Signing Certificate is the Basic Edition in MeSign E-sign Service because we fully know it is not very easy for you from applying certificate to using the certificate and manage the certificate.
Your demand is to digitally sign the PDF documents other than buying the certificate.
Learn more about how to buy and use Adobe Trusted PDF Signing Certificate