Set page content height dynamically in crystal

I am using crystal report for printing details. I have two issues while printing.

1. Set page content height dynamically

I want to set the page content height dynamically. We can set the page height and width from Design -> Page setup -> Page options -> Set Horizontal and Vertical values.

What is happening in my case is, I am using crystal report to print barcodes. When the page height is big, it prints empty barcodes which I don't want. I want to set the page content height based on the number of barcodes I am going to print. How can I do this?

2. Top margins not working

I am NOT giving top margin but when I print the report using my printer, there are some of the space being left from the top. My printer details are as below.

Printer name: Barcod printer

Model: tsc ttp/tdp-243(E)

What can be the problem with the top margin?

Can anybody help me solve these two issues?