If you need additional space for more annotations, PDF Annotator is able to increase page sizes by adding margins.
Add Margins
Select Edit
Page
Add Margins to open the Add Margins dialog. Now select the Additional Margins and a Page Range.
By providing a Page Range, you can add margins to all pages, or only specific pages (for example a Page Selection).
See also
Page URL: http://www.GRAHL-software.com/pdfannotator/std/en/help/index.html?pagesaddmargins.htm