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-rw-r--r--include/qpdf/QPDFWriter.hh21
1 files changed, 14 insertions, 7 deletions
diff --git a/include/qpdf/QPDFWriter.hh b/include/qpdf/QPDFWriter.hh
index e8b744d2..e2f731d3 100644
--- a/include/qpdf/QPDFWriter.hh
+++ b/include/qpdf/QPDFWriter.hh
@@ -219,13 +219,20 @@ class QPDFWriter
QPDF_DLL
void copyEncryptionParameters(QPDF&);
- // Set up for encrypted output. Disables stream prefiltering and
- // content normalization. Note that setting R2 encryption
- // parameters sets the PDF version to at least 1.3, setting R3
- // encryption parameters pushes the PDF version number to at least
- // 1.4, setting R4 parameters pushes the version to at least 1.5,
- // or if AES is used, 1.6, and setting R5 or R6 parameters pushes
- // the version to at least 1.7 with extension level 3.
+ // Set up for encrypted output. User and owner password both must
+ // be specified. Either or both may be the empty string. Note
+ // that qpdf does not apply any special treatment to the empty
+ // string, which makes it possible to create encrypted files with
+ // empty owner passwords and non-empty user passwords or with the
+ // same password for both user and owner. Some PDF reading
+ // products don't handle such files very well. Enabling
+ // encryption disables stream prefiltering and content
+ // normalization. Note that setting R2 encryption parameters sets
+ // the PDF version to at least 1.3, setting R3 encryption
+ // parameters pushes the PDF version number to at least 1.4,
+ // setting R4 parameters pushes the version to at least 1.5, or if
+ // AES is used, 1.6, and setting R5 or R6 parameters pushes the
+ // version to at least 1.7 with extension level 3.
QPDF_DLL
void setR2EncryptionParameters(
char const* user_password, char const* owner_password,