How does ps adjust the finished picture to A3 size?

Ps The method and steps for adjusting the finished picture to A3 size are as follows:

Tools/materials: computer, PS

Application program.

1, first open the computer, enter the computer desktop, and then double-click to open PS.

2. Then select a picture and click Open.

3. Then click the image at the top of the interface, and then click the image size in the pop-up menu.

4. Then set the size to 420× 297mm, which is the standard size of a3 paper. Uncheck the constraint before, and then click OK.

5. The final image becomes a3 size, and the setting is completed.