Update readme

README.md

@@ -11,12 +11,16 @@ https://www.ghostscript.com/download
 http://blog.alivate.com.au/poppler-windows
 
 **Linux**:  
-`sudo apt install ghostscript`  
-`sudo apt install poppler-utils`
+```
+sudo apt install ghostscript
+sudo apt install poppler-utils
+```
 
 **Mac**:  
-`brew install ghostscript`  
-`brew install poppler`
+```
+brew install ghostscript
+brew install poppler
+```
 
 Then
 
@@ -32,14 +36,20 @@ pip install -e pdfunlock
 Search for pdfs inside 'pdf_folder', then create new unlocked versions
 of the pdfs with the the suffix '-unlocked.pdf':
 
-`> pdfunlock pdf_folder`
+```
+pdfunlock pdf_folder
+```
 
 Search for pdfs inside 'pdf_folder', then unlock the pdfs and overwrite
 the original versions.
 
-`> pdfunlock pdf_folder -o`
+```
+pdfunlock pdf_folder -o
+```
 
 Search recursively for pdfs inside 'pdf_folder' and all subfolders,
 then unlock the pdfs and overwrite the original versions.
 
-`> pdfunlock pdf_folder -o -r`
+```
+pdfunlock pdf_folder -o -r
+```