Different printers have different printable areas. Most of them have a border round the edge of the paper that they do not print onto.
This issue is especially noticeable for printers printing onto different paper sizes and has caused problems for people in the past. 
In the UK and Europe the commonly used paper size is A4. 210mm x 297mm. In the US, letter size is more commonly used.  8.5 by 11 inches (215.9 mm × 279.4 mm)
To ensure that everyone can print out the models on this website I’m gathering information to establish a common printable area which can be used by most people. If you would like to help, please download and print out this page, making sure that the print is set to full size or 100% then let me know where the printing stops either by email or in the comments. Please also let me know the printer type and the paper size you are using.
Thanks for your help!