diff --git a/crates/automation/src/printing.rs b/crates/automation/src/printing.rs
index 19cd48ef4..39cd45760 100644
--- a/crates/automation/src/printing.rs
+++ b/crates/automation/src/printing.rs
@@ -6,6 +6,22 @@ use serde_json::{Value, json};
 
 use crate::{Args, Automation, Result, ToolError, failed, write_atomic};
 
+/// The job's two-sided setting for `doc_print`'s `duplex`: `printer` sends none, so the printer's
+/// own default applies (as the Print dialog's Printer default, #2422), except that cut and stack
+/// needs single-sided sheets.
+fn duplex(value: &str, cut_stack: bool) -> Result<Option<spool::Duplex>> {
+    Ok(match value {
+        "printer" if cut_stack => Some(spool::Duplex::Off),
+        "printer" => None,
+        "off" => Some(spool::Duplex::Off),
+        "long-edge" if cut_stack => return Err(bad("cut-and-stack printing needs duplex off (single-sided sheets)")),
+        "short-edge" if cut_stack => return Err(bad("cut-and-stack printing needs duplex off (single-sided sheets)")),
+        "long-edge" => Some(spool::Duplex::LongEdge),
+        "short-edge" => Some(spool::Duplex::ShortEdge),
+        d => return Err(bad(format!("unknown duplex {d:?}"))),
+    })
+}
+
 fn bad(m: impl Into<String>) -> ToolError {
     ToolError::InvalidArgs(m.into())
 }
@@ -92,9 +108,7 @@ impl Automation {
             },
             l => return Err(bad(format!("unknown layout {l:?}"))),
         };
-        if matches!(layout, Layout::Multiple { order: PageOrder::CutStack, .. }) && a.opt_str("duplex")?.unwrap_or("off") != "off" {
-            return Err(bad("cut-and-stack printing needs duplex off (single-sided sheets)"));
-        }
+        let duplex = duplex(a.opt_str("duplex")?.unwrap_or("off"), matches!(layout, Layout::Multiple { order: PageOrder::CutStack, .. }))?;
         if a.opt_str("order")? == Some("cut-stack") && !matches!(layout, Layout::Multiple { .. }) {
             return Err(bad("cut-stack order needs layout multiple"));
         }
@@ -153,12 +167,7 @@ impl Automation {
                     printer: if printer == "default" { None } else { Some(printer.to_string()) },
                     copies: a.opt_int("copies")?.unwrap_or(1).clamp(1, 999) as u32,
                     collate: a.opt_bool("collate")?.unwrap_or(true),
-                    duplex: Some(match a.opt_str("duplex")?.unwrap_or("off") {
-                        "off" => spool::Duplex::Off,
-                        "long-edge" => spool::Duplex::LongEdge,
-                        "short-edge" => spool::Duplex::ShortEdge,
-                        d => return Err(bad(format!("unknown duplex {d:?}"))),
-                    }),
+                    duplex,
                     scaling: spool::Scaling::Exact,
                     grayscale: a.opt_bool("grayscale")?.unwrap_or(false),
                     title: name,
@@ -181,3 +190,21 @@ impl Automation {
         Ok(out)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// `printer` leaves two-sided to the printer's own default (#2422); cut and stack still asks
+    /// for single-sided sheets, and refuses an explicit edge.
+    #[test]
+    fn duplex_printer_leaves_two_sided_to_the_printer() {
+        assert_eq!(duplex("printer", false).ok(), Some(None));
+        assert_eq!(duplex("printer", true).ok(), Some(Some(spool::Duplex::Off)));
+        assert_eq!(duplex("off", false).ok(), Some(Some(spool::Duplex::Off)));
+        assert_eq!(duplex("long-edge", false).ok(), Some(Some(spool::Duplex::LongEdge)));
+        assert_eq!(duplex("short-edge", false).ok(), Some(Some(spool::Duplex::ShortEdge)));
+        assert!(duplex("long-edge", true).is_err());
+        assert!(duplex("sideways", false).is_err());
+    }
+}
diff --git a/crates/automation/src/tools.rs b/crates/automation/src/tools.rs
index 5e89aef78..58e4fa508 100644
--- a/crates/automation/src/tools.rs
+++ b/crates/automation/src/tools.rs
@@ -507,7 +507,7 @@ pub fn tools() -> Vec<ToolDef> {
                 "printer": { "type": "string" },
                 "copies": { "type": "integer", "minimum": 1, "maximum": 999 },
                 "collate": { "type": "boolean" },
-                "duplex": { "type": "string", "enum": ["off", "long-edge", "short-edge"] },
+                "duplex": { "type": "string", "enum": ["off", "long-edge", "short-edge", "printer"], "description": "Two-sided printing (default off); printer sends no setting, so the printer's own default applies." },
                 "grayscale": { "type": "boolean" },
                 "as_image": { "type": "boolean", "description": "Print as image (Acrobat's Advanced Print Setup): every page rendered to a picture at dpi before it is placed on the paper, for printers that skip text, shading or transparency; the print is no longer searchable text, and with grayscale the pictures are grey." },
                 "dpi": { "type": "number", "minimum": 72, "maximum": 600, "description": "Resolution for as_image (default 300)." },
diff --git a/crates/automation/tests/automation.rs b/crates/automation/tests/automation.rs
index 1e662d8f3..66f968a43 100644
--- a/crates/automation/tests/automation.rs
+++ b/crates/automation/tests/automation.rs
@@ -5300,6 +5300,9 @@ fn cut_stack_printing_through_tools() {
     }
     assert!(matches!(a.call("doc_print", &json!({"doc": doc, "order": "cut-stack", "path": "refused.pdf"})), Err(ToolError::InvalidArgs(_))));
     assert!(!dir.join("refused.pdf").exists());
+    // The printer's own two-sided default isn't refused: cut and stack sends single-sided (#2422).
+    ok(&mut a, "doc_print", json!({"doc": doc, "layout": "multiple", "order": "cut-stack", "duplex": "printer", "path": "printer-default.pdf"}));
+    assert!(dir.join("printer-default.pdf").exists());
     assert!(a.call("doc_print", &json!({"doc": doc, "layout": "multiple", "order": "cut-stack", "path": "../escaped.pdf"})).is_err());
     let _ = std::fs::remove_dir_all(dir);
 }
diff --git a/parity/acrobat-features.toml b/parity/acrobat-features.toml
index 7ecd6b403..99550a9ad 100644
--- a/parity/acrobat-features.toml
+++ b/parity/acrobat-features.toml
@@ -8020,8 +8020,8 @@ milestone = "M10"
 status = "shipped"
 commands = ["print.dialog"]
 tools = ["doc_print"]
-evidence = ["crates/print/src/tests.rs::spooler_arguments_and_printer_list", "crates/ui-egui/src/print_ui.rs::two_sided_follows_the_printer_until_chosen"]
-notes = "long/short edge via the spooler: lp -o sides=…, and the Windows driver's Duplex setting. Two-sided starts at Printer default, as in Acrobat: nothing is sent, so the printer's own default (its Properties) applies until Off or an edge is chosen. Missing: the document's /ViewerPreferences /Duplex preset isn't read yet"
+evidence = ["crates/print/src/tests.rs::spooler_arguments_and_printer_list", "crates/ui-egui/src/print_ui.rs::two_sided_follows_the_printer_until_chosen", "crates/automation/src/printing.rs::duplex_printer_leaves_two_sided_to_the_printer"]
+notes = "long/short edge via the spooler: lp -o sides=…, and the Windows driver's Duplex setting. Two-sided starts at Printer default, as in Acrobat: nothing is sent, so the printer's own default (its Properties) applies until Off or an edge is chosen (doc_print: duplex \"printer\"). Missing: the document's /ViewerPreferences /Duplex preset isn't read yet"
 
 [[feature]]
 id = "print.n-up"