Answer
By using a
vector-based file (which is scalable), you can create a smaller design that is easier to work with and can then be printed in a larger size.
If your design program is crashing because your file is too large, we recommend reducing the file to ¼ or ½ of the final print size. Use 300 dpi to ensure quality, and flatten the file so it’s easier to upload. Save the file as a .PDF, which maintains the file’s settings but reduces its overall size.
For more information on this topic, review
How-To Design a Large File In Photoshop.