diff --git a/firefox_preferences/dark_reader_pdf.txt b/firefox_preferences/dark_reader_pdf.txt
new file mode 100644
index 00000000..77266da0
--- /dev/null
+++ b/firefox_preferences/dark_reader_pdf.txt
@@ -0,0 +1,4 @@
+# To get dark reader on pdf in firefox, simply hit F12, and paste this into the console:
+
+javascript:(function(){viewer.style = 'filter: grayscale(1) invert(1) sepia(1) contrast(75%)';})()
+