Update readme

README.md

@@ -4,10 +4,14 @@ __pdf_unlock.py__ removes security features from pdfs, to allow unrestricted pri
 
 ## Installation ##
 
-[Ghostscript](https://ghostscript.com) is required. Windows users will have to add Ghostscript directory to the `PATH` environment variable manually, eg:
+[Ghostscript](https://ghostscript.com) and [Poppler](https://poppler.freedesktop.org) are required.
 
-`C:\Program Files\gs\gs9.21\bin`
+Windows users will have to add the binary directories to the `PATH` environment variable manually, eg:
 
+```
+C:\Program Files\gs\gs9.21\bin
+C:\Program Files\poppler\bin
+```
 ## Usage ##