Adding Multiple file in Document

When I am trying to add more than two file in Document number, it restrict me to add only two documents.  Configuration settings take me to Document management---Define Document Type--Select the Check Box--Use KPro. By using this Check Box active, I am able to upload more than 2 files in Document.

Now the Question form my end is.

We already have documents for this Document Type. Will there be impact on existing documents after activation. Any OSS Note will be great.

Or SAP help-link related to same.