[afranchuk]

For what it's worth, Firefox has had most of these features built into their PDF.js viewer for a while. I believe signatures were recently added. I'm not sure whether there's capability to remove pages or merge PDFs, though.

[rocketvole]

pdf.js is also available as an extension on chromium based browsers.

I've found that scrolling on pdfs on a high dpi screen using the built in chromium pdf reader is extremely laggy so this has always been a must-have extension for me.