ppi stands for pixels per inch, so what you really need to figure out is what size an A4 print is in pixels at 300 ppi. When I go to Photoshop and create a new image, I am given the option of selecting a default size. There it says that A4 is 2480 x 3508 pixels. If we play like it is a fraction, like 2480/3508 and reduce it to lowest terms, we come up with a ratio. Well, I don't kow about lowest terms but it does look like both numbers can be divided by 4, which gives 620 x 877. In UF, don't use the pull down menu in the image size tab. Deselect the "maintain aspect ratio" button and key in the values of 620 x 877. From there on select the "maintain aspect ratio" button and let UF figure it out.