Tally uses HTML to generate your PDF documents.  This allows for great flexibility although can result in an anomaly if you've got extra spaces in your additional text box, this can result in your documents appearing to shrink to fit on the page.  To solve this problem you'll need to modify your additional text.

Removing Additional Spaces

To solve this problem, go to Settings > PDF Themes > Select your current theme > Misc Options > Use the additional text to remove the extra spaces, you can use line breaks instead in our new PDF generator.