I'm building a node.js app on Bluemix that should take a pdf file as request and then grey out (blank) some part of the pdf file. And also here the pdf file is the same for all, and the area we need to blank out will be fixed. So can anybody suggest an npm module that can perform this kind of functionality?
I suggest you to try HummusPDF. Specifically take a look at the Hummus - Modification page, that explains how to edit existing PDF documents. In your case you could try to use the feature that allows to draw shapes.
来源：https://stackoverflow.com/questions/39362845/is-there-an-npm-module-to-modify-a-pdf-file-in-node-js