[Question]: How to configure the ppd with watermark?

[hustliyilin]

I want to add the watermark when printing files with cups-pdf or other printers. The current idea is to modify the ppd file of the corresponding printer on the host side. According to the guide of the repository, I added the corresponding configuration to the ppd file(/usr/share/cups/model/CUPS-PDF_opt.ppd), as shown below：

*OpenUI WatermarkText/Watermark Text: PickOne
*OrderDependency: 100 AnySetup *WatermarkText
*DefaultWatermarkText: Test
*WatermarkText Test: "watermark test"
*WatermarkText Draft: "<</cupsString1(Draft)>>setpagedevice"
*CloseUI: *WatermarkText

However, the printed files don't have watermarks (not effective). I would like to ask if there is any wrong configuration. I look forward to your reply. Thank you very much.