Hi

I think you can generate pdf using base64 data stream and view the pdf using Activity with following steps.

Step 1: Java

String s = tools.getParamValue("Data").toString();  //Data is the base64 encoded string (Parameter)
byte[] byteArray = new com.pega.pegarules.pub.util.Base64Util().decodeToByteArray(s);
tools.putParamValue("Data",byteArray);
tools.sendFile(byteArray, "Example.pdf",false, null, false);

This will view pdf in a new window.

if you want to download the file 

Step 1: Java 

String s = tools.getParamValue("Data").toString();         
byte[] byteArray = new com.pega.pegarules.pub.util.Base64Util().decodeToByteArray(s); 
tools.putParamValue("Data",byteArray);

Step 2: Call Code-Pega-PDF.View

PDFName : Example.pdf

PDFDocument : Param.Data 

Hope this helps.