Update 'README.md'

README.md

@@ -12,3 +12,11 @@ My cheat sheet for commands I have trouble remembering.
 
 ## Recursively unzip
 ```while [ "`find . -type f -name '*.zip' | wc -l`" -gt 0 ]; do find -type f -name "*.zip" -exec unzip -- '{}' \; -exec rm -- '{}' \;; done```
+
+## Merge PDF files
+
+#### Ghostscript
+```gs -dNOPAUSE -sDEVICE=pdfwrite -sOUTPUTFILE=mergedfile.pdf -dBATCH file1.pdf file2.pdf```
+
+#### ImageMagick
+```convert file1.pdf[0-1] file2.pdf mergedfile.pdf```