Allow PDF 2.x

owl.py

@@ -386,7 +386,7 @@ def validate_attachment(form, field):
 def is_pdf(f):
     f.seek(0)
     header = f.read(9)
-    return len(header) == 9 and header[:7] == b'%PDF-1.'
+    return len(header) == 9 and (header[:7] == b'%PDF-1.' or header[:7] == b'%PDF-2.')
 
 
 def is_utf8(f):