Adding PDF Engine Features

Each new PDF engine capability (bookmarks, watermark, stamp, embed, etc.) 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. Skip this step and make run falls back to the default defined in pdfengines.go, which may not include the new engine.

Every --pdfengines-*-engines flag registered in pdfengines.go needs two additions:

1. A variable in the Makefile's variable block (around line 60-70):

   makefileCopy

   PDFENGINES_<FEATURE>_ENGINES=<default engines>
   

2. A 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

Rotate was added with two engines (pdfcpu and pdftk):

Makefile (variable block):

PDFENGINES_ROTATE_ENGINES=pdfcpu,pdftk

compose.yaml (command args):

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