Impozycjoner program distinguishes the terms: use and PDF-page placed on the sheet. Use - is a potential place on the sheet, in which it will be fitted - or otherwise - on which the PDF-page will be placed. The parameters of use are: horizontal (H) and vertical (V) net, horizontal and vertical gross, bleeds and rotation. Uses are placed on a sheet in a table with a defined number of columns and rows.
Net size is the size of the use after printing the sheet and cutting it. Gross sizes are net sizes increased by appropriate bleed values.
Bleed is additional area around the net size. Each use has 4 bleeds: top, bottom, left and right (for leaflets imposition). When impositioning books, the left fall is called the internal bleed (or cutter), and the right fall is dropped by the outer one - for the use destined for the odd side. For use for an even side - the opposite (symmetrically).
The use has also defined the rotation angle by which it will be rotated on the imposition sheet. This is important information, because the use of vertical orientation (width less than height) rotated by 90 ° is not the same as the horizontal use, unrotated.
The net and gross size markers drawn by the program determine the appropriate size of the use, not the pages placed on the sheet. Most often these are identical concepts. The use, however, has no content, it is only an area in which a specific PDF-page can be inserted (or not - because the use can be "empty").
Use - this is a place on the sheet in which the selected PDF-page is placed in a suitable way. Use - this is not a PDF-page (and vice versa).
Sometimes, however, pages placed in the area of use are of different sizes than use.
If the dimensions of the TrimBox are larger than the size of the use, then occupying the use - the TrimBox of the page is centered in it. Centering refers to the dimension of the larger TrimBox (one or both).
This behavior of the program makes it much easier to edit PDF-files in which the net size (TrimBox) is undefined. In this case, the size of the CropBox is taken for the net size, and if it cannot be find in the file, it is the size of the MediaBox. It is only important to keep the contents of the file centered on the PDF-page.
Example: different definitions of size and position of TrimBox
6 PDF-files with different definition of TrimBox - sizes and location. In all files, the target area to be cut out of the sheet and passed to the customer is marked with a dotted light blue line and has the same size (74x105 mm).
5 files (from A7_sample_1.pdf to A7_sample_5.pdf) have one thing in common - the area to be cut from the sheet lies centrally in the middle of the TrimBox area (and if TrimBox is not specified, it is in the middle of the CropBox or MediaBox area).
After loading the files into the program and after setting the size of use equal to 74x105 mm, in several files the program shows in the Imposition Pages Table that the read size TrimBox is larger than the size of the use. Despite this, the user of the program does not have to do anything unnecessary - just place the page on the sheet.
Only file No. 6 (A7_sample_6.pdf) requires adjustment of the location and size of the TrimBox. In this file, the size of the TrimBox is not specified, and the area designated to be cut after printing the area does not lie centrally on the page.
If the use’s dimensions (both or one of them) are greater than the net dimensions (TrimBox) of the page placed in it, then the page can be aligned with one of the corners of the site (menu Align the gross area is the corner of the use...) - concerns the dimension use larger than the appropriate page size.
In the book imposition module - pages placed in the field of use are always centered.