Adding PDF Engine Features

Each new PDF engine capability (e.g., bookmarks, watermark, stamp, embed) requires a matching Makefile entry. The Makefile variables control which engines are passed to Gotenberg at make run and make test-integration time (via compose.yaml). If you skip this step, the flag still works when set manually, but make run falls back to the default defined in pdfengines.go, which may not include the new engine.

Every --pdfengines-*-engines flag registered in pkg/modules/pdfengines/pdfengines.go must have a corresponding variable and flag in the Makefile:

1. Add a variable in the Makefile's variable block (around line 60 to 70):
   makefileCopy

   PDFENGINES_<FEATURE>_ENGINES=<default engines>
   

2. Add the flag in compose.yaml's command args:
   yamlCopy

   - "--pdfengines-<feature>-engines=${PDFENGINES_<FEATURE>_ENGINES}"
   

The default value must match the fs.StringSlice(...) call for that flag in pdfengines.go.

Example: Rotate

The rotate feature was added with two engines (pdfcpu and pdftk). Here is what the additions look like:

Makefile (variable block):

PDFENGINES_ROTATE_ENGINES=pdfcpu,pdftk

compose.yaml (command args):

- "--pdfengines-rotate-engines=${PDFENGINES_ROTATE_ENGINES}"