From the "least relevant" way to communicate with a customer to the "most relevant", here are the different levels of how content can be customized within a document:

Static:

 

This is a "one size fits all" marketing message. Your marketing message is "mass-produced" using conventional offset printing and every customer will receive the same message, regardless of their relationship or profitability to your company.

Personalized:

 

Each customer's name and address will appear on each document to attract their attention, but the marketing message is static and exactly the same for each and every customer, regardless of their relationship or profitability to your company.