Update readme

README.md

@@ -4,14 +4,27 @@ __pdf_unlock.py__ removes security features from pdfs, to allow unrestricted pri
 
 ## Installation ##
 
-[Ghostscript](https://ghostscript.com) and [Poppler](http://blog.alivate.com.au/poppler-windows) are required.
+[Ghostscript](https://ghostscript.com) and [Poppler](https://poppler.freedesktop.org/) are required.
 
-Windows users will have to add the binary directories to the `PATH` environment variable manually, eg:
+**Windows**:  
+https://www.ghostscript.com/download  
+http://blog.alivate.com.au/poppler-windows
+
+**Linux**:  
+`sudo apt install ghostscript`  
+`sudo apt install poppler-utils`
+
+**Mac**:  
+`brew install ghostscript`  
+`brew install poppler`
+
+Then
 
 ```
-C:\Program Files\gs\gs9.21\bin
-C:\Program Files\poppler\bin
+pip install tqdm
 ```
+
+
 ## Usage ##