preserve /Encrypt for documents with streamed xrefs

If /Encrypt is not present on an updated xref of an encrypted document,
that document can no longer be opened. This is required for incremental
saving.

Note: Streams aren't encrypted by pdf_write_document and can't thus
currently be appended to an encrypted document. In that case, saving
non-incrementally will produce a working (non-encrypted) document.

1 files changed, 7 insertions, 0 deletions

diff --git a/source/pdf/pdf-write.c b/source/pdf/pdf-write.c
index 3ae6796e..579204ca 100644
--- a/source/pdf/pdf-write.c
+++ b/source/pdf/pdf-write.c
@@ -1919,6 +1919,13 @@ static void writexrefstream(pdf_document *doc, pdf_write_options *opts, int from
 			obj = pdf_dict_gets(pdf_trailer(doc), "ID");
 			if (obj)
 				pdf_dict_puts(dict, "ID", obj);
+
+			if (opts->do_incremental)
+			{
+				obj = pdf_dict_gets(pdf_trailer(doc), "Encrypt");
+				if (obj)
+					pdf_dict_puts(dict, "Encrypt", obj);
+			}
 		}
 
 		pdf_dict_puts_drop(dict, "Size", pdf_new_int(doc, to));