I am thinking of adding border to my photos before I send them for printing (4R - ratio 2:3). My files are all in 2:3 ratio and would like to add about 100 pixels for the border where the final pixel is not 2:3 anymore. eg 1200 x 1800 with 100 pixels more for border, it will become 1300 x 1900 which is not 2:3 anymore.
Is there anyway I can do it by maintaining the ratio with the border added on? I know the printer can add for me the white border but I would like to type something on the border so I need to do it by myself.
Thanks in advance!