It doesn't matter if you can't print it, it doesn't matter if you download it and save it on that disk. Also, it doesn't matter if the computer shows the drawings clearly. PDF can be adjusted to large or small, regardless of whether it can be printed or not.

When you want to print, click Print, and a prompt box will appear asking what printing you want to set, regardless of the size. Your problem should only happen if your first picture is not set. Also, you said that the handwriting is clear and the background color is ok. Are you sure it's a blank sheet of paper?