Improve testing and error handling around operating before processing

1 files changed, 3 insertions, 1 deletions

diff --git a/include/qpdf/qpdf-c.h b/include/qpdf/qpdf-c.h
index cf32976f..886e521f 100644
--- a/include/qpdf/qpdf-c.h
+++ b/include/qpdf/qpdf-c.h
@@ -113,7 +113,9 @@ extern "C" {
     char const* qpdf_get_qpdf_version();
 
     /* Returns dynamically allocated qpdf_data pointer; must be freed
-     * by calling qpdf_cleanup.
+     * by calling qpdf_cleanup. You must call qpdf_read or one of the
+     * other qpdf_read_* functions before calling any function that
+     * would need to operate on the PDF file.
      */
     QPDF_DLL
     qpdf_data qpdf_init();