Some clarifications first.
I am aware that CMYK is a Colour Gamut used for Printing
@User287001 (btw, this user should put a name behind all that knowledge) already said that it is not a gamut.
CMYK is several things.
A. It is a Color model, generally speaking using primary subtractive colors to generate an image based on a light substrate. The K is ...
Let me go step by step here.
Say you have a vector image you open up in both Photoshop and Illustrator in DINA3 and 300ppi.
A vector image will stay vector on Illustrator (1), this means that the 300PPI will have no effect. This setting on Illustrator is when it needs to actually rasterize something, some shadow for example. This means that if it is ...
As you are new to graphic design for now just set up the background as another color and let them print it.
So, do not worry about Ink, business are used to print things in full size on their printer, a photo, a poster, so it is part of the job.
Having a paper different from the background can be tricky.
First of all, you need to be sure that the paper ...