ajust the size of the document to the image

[smartisez]

hello everyone, 

i'm new to affinity photo and i can't find how to ajust to the size of a pictures 

i usually draw comics on a A4 size document, then i want to isolate each ''square'' of my comics and put them in a different document. So i create a new document but when i paste the square of my comics it is smaller than the size of the new document, so i have to ajust it manually but it's not consistent and takes too much time. is it possible to ajust fast the size of the document to the size of the ''square'' so it doesn't have white border when i save it as a pictures ? 

thanks you in advence 

[R C-R]

There are several ways to do this but one of the easiest is to select all the elements of the comics, copy them, & use File > New from Clipboard to create the new document.