Generate bleed by pattern extension
When a production file is a repeatable pattern, bleed can be created in a 100% accurate way using pdfToolbox. To do so, use the "Generate bleed by pattern extension" fixup.
This only works if the input PDF file is perfectly repeatable as a pattern. This means that duplicating the input PDF file horizontally and/or vertically creates a perfectly extended pattern, without visible breaks.
Fixup parameters
The fixup has ony a few basic parameters:
Set the required amount of bleed on all sides and then run the fixup. An example of the end result of running this fixup is shown below:
Here, 10 mm of bleed was created around the original PDF file. The type of pattern and percentage of shift (for half-drop, or brick patterns) doesn't matter, as long as the input PDF file is properly repeatable.
Example
You can test this yourself by downloading the below PDF file and Process Plan.