diff --git a/README.md b/README.md
index f2f6adf..574e032 100644
--- a/README.md
+++ b/README.md
@@ -142,6 +142,14 @@
 you see failures, it can be a good idea to run the tests on the tip-of-tree
 checkout to see if the same failures appear.
 
+## Embedding PDFium in your own projects
+
+The public/ directory contains header files for the APIs available for use by
+embedders of PDFium. We endeavor to keep these as stable as possible.
+
+Outside of the public/ directory, code may change at any time, and embedders
+should not directly call these routines.
+
 ## Code Coverage
 
 Code coverage reports for PDFium can be generated in Linux development