What is a Trimbox?

A PDF describes the content and appearance of one or more pages and also defines the physical size of those pages. There can be up to five different definitions in a PDF related to the size of its pages: MediaBox, CropBox, BleedBox, TrimBox and ArtBox. These are called the page boxes or boundary boxes. PDF boxes describe the page geometry of a PDF. They are used frequently in the printing industry.

The TrimBox

The TrimBox has a special meaning when it comes to printing a PDF. This is the key page box because the TrimBox defines the final page size after trimming. If it is not set, the TrimBox will be the same as the CropBox. Except for the ArtBox, the TrimBox is usually the smallest page box. To view a PDF at its final (trim) size, set the CropBox to match the TrimBox. Some systems do this by default.

Read more about the other PDF boxes in the following article: What are PDF boxes?