PDF files created with Wicked PDF would not be stamped / numbered correctly

[boazsegev]

This issue was reported by Saba.

Looking into the issue, I discovered that the Wicked PDF's engine ( wkhtmltopdf ) doesn’t wrap the PDF content streams correctly.

to be more technical:

Immediately at the start of each page’s content stream, wkhtmltopdf creates a 'transformation' to the drawing engine (using the PDF command: 0.060000000 0 0 -0.060000000 28.3200000 813.679999 cm)…

This transformation isn’t wrapped in a container (the PDF commands q and Q), so that the transformation effects all the content streams as well as the original content.

The end result is that the stamped content (page numbering / watermark / overlaid page) is resized and appears inverted (upside down and mirror like) in the top left corner of the PDF page - which is an unexpected bug caused by this malformed PDF.

This was fixed by injecting a wrapper around the all the content streams, each time content is injected to an existing PDF page.