diff --git a/crates/vectorcraft-format/README.md b/crates/vectorcraft-format/README.md
index e69a3ac9..4d1ea34e 100644
--- a/crates/vectorcraft-format/README.md
+++ b/crates/vectorcraft-format/README.md
@@ -34,6 +34,12 @@ reads one, and `Contents::read(json)` reads `format`, `version`, `document`, `im
 `profiles` and skips `generator`, `preview` and `pdf` as the JSON is read, so their base64 is not
 buffered or kept. Both read the files VectorCraft opens:
 
+`Contents::read_with_pdf_preference(json)` returns `(contents, pdf_compatible)` in that same
+envelope pass. It reads an optional boolean `pdfCompatible`, falling back to a non-null `pdf`
+member when the preference is absent or null. It neither retains nor decodes the PDF payload.
+Repeated PDF members use their last value, and the array form returns false. A non-boolean
+preference is an error in this opt-in method; `Contents::read` keeps ignoring that field.
+
 - They return `ReadError::Envelope(Error::Format)` for another format name and
   `ReadError::Envelope(Error::TooNew)` for a version newer than `VERSION`, after the JSON reads;
   `ReadError::Json` otherwise.
diff --git a/crates/vectorcraft-format/src/lib.rs b/crates/vectorcraft-format/src/lib.rs
index 8b4892f2..3c9ff4e1 100644
--- a/crates/vectorcraft-format/src/lib.rs
+++ b/crates/vectorcraft-format/src/lib.rs
@@ -188,18 +188,30 @@ impl<D> File<D> {
     where
         D: Deserialize<'de>,
     {
-        read(json, true)
+        read(json, true, false).map(|(file, _)| file)
     }
 }
 
 /// [`File::read`] and [`Contents::read`]; `keep` is false for [`Contents`], which skips
 /// `generator`, `preview` and `pdf` without keeping them.
-fn read<'de, D: Deserialize<'de>>(json: &'de [u8], keep: bool) -> Result<File<D>, ReadError> {
+fn read<'de, D: Deserialize<'de>>(json: &'de [u8], keep: bool, read_pdf: bool) -> Result<(File<D>, bool), ReadError> {
     let mut de = serde_json::Deserializer::from_slice(json);
-    let file = serde::Deserializer::deserialize_struct(&mut de, "File", MEMBERS, FileVisitor { keep, document: PhantomData })?;
+    let mut pdf = PdfPreference::default();
+    let file = serde::Deserializer::deserialize_struct(
+        &mut de,
+        "File",
+        MEMBERS,
+        FileVisitor { keep, pdf: read_pdf.then_some(&mut pdf), document: PhantomData },
+    )?;
     de.end()?;
     file.check()?;
-    Ok(file)
+    Ok((file, pdf.preference.unwrap_or(pdf.present)))
+}
+
+#[derive(Default)]
+struct PdfPreference {
+    preference: Option<bool>,
+    present: bool,
 }
 
 /// The members of a file, in the order of the array form.
@@ -219,12 +231,13 @@ struct Members<D> {
 }
 
 /// Reads a [`File`] from a JSON object or array.
-struct FileVisitor<D> {
+struct FileVisitor<'a, D> {
     keep: bool,
+    pdf: Option<&'a mut PdfPreference>,
     document: PhantomData<D>,
 }
 
-impl<'de, D: Deserialize<'de>> Visitor<'de> for FileVisitor<D> {
+impl<'de, D: Deserialize<'de>> Visitor<'de> for FileVisitor<'_, D> {
     type Value = File<D>;
 
     fn expecting(&self, f: &mut fmt::Formatter) -> fmt::Result {
@@ -236,7 +249,7 @@ impl<'de, D: Deserialize<'de>> Visitor<'de> for FileVisitor<D> {
         Ok(File { format, version, generator: None, preview: None, profiles, pdf: None, document, images })
     }
 
-    fn visit_map<A: MapAccess<'de>>(self, mut map: A) -> Result<File<D>, A::Error> {
+    fn visit_map<A: MapAccess<'de>>(mut self, mut map: A) -> Result<File<D>, A::Error> {
         let (mut format, mut version, mut document, mut images, mut profiles) = (None, None, None, None, None);
         let (mut generator, mut preview, mut pdf) = (None, None, None);
         while let Some(key) = map.next_key::<String>()? {
@@ -249,6 +262,16 @@ impl<'de, D: Deserialize<'de>> Visitor<'de> for FileVisitor<D> {
                 "generator" if self.keep => generator = map.next_value::<Lenient<String>>()?.0,
                 "preview" if self.keep => preview = map.next_value::<Lenient<Image>>()?.0,
                 "pdf" if self.keep => pdf = map.next_value::<Lenient<Image>>()?.0,
+                "pdfCompatible" if self.pdf.is_some() => {
+                    if let Some(state) = self.pdf.as_mut() {
+                        state.preference = map.next_value::<Option<bool>>()?;
+                    }
+                }
+                "pdf" if self.pdf.is_some() => {
+                    if let Some(state) = self.pdf.as_mut() {
+                        state.present = map.next_value::<Option<IgnoredAny>>()?.is_some();
+                    }
+                }
                 _ => {
                     map.next_value::<IgnoredAny>()?;
                 }
@@ -339,10 +362,25 @@ impl<D> Contents<D> {
     where
         D: Deserialize<'de>,
     {
-        let File { format, version, document, images, profiles, .. } = read(json, false)?;
+        let (file, _) = read(json, false, false)?;
+        let File { format, version, document, images, profiles, .. } = file;
         Ok(Self { format, version, document, images, profiles })
     }
 
+    /// Reads the document and its saved PDF preference in one envelope pass, without
+    /// keeping or decoding the PDF payload. A non-null `pdf` supplies the fallback when
+    /// `pdfCompatible` is absent or null. Repeated members use their last value; arrays
+    /// have no PDF preference and return false. A non-boolean preference is an error.
+    /// The existing [`Self::read`] continues to ignore that optional preference.
+    pub fn read_with_pdf_preference<'de>(json: &'de [u8]) -> Result<(Self, bool), ReadError>
+    where
+        D: Deserialize<'de>,
+    {
+        let (file, compatible) = read(json, false, true)?;
+        let File { format, version, document, images, profiles, .. } = file;
+        Ok((Self { format, version, document, images, profiles }, compatible))
+    }
+
     /// [`File::is_legacy`].
     pub fn is_legacy(&self) -> bool {
         self.format == LEGACY_EXTENSION
diff --git a/crates/vectorcraft-format/tests/envelope.rs b/crates/vectorcraft-format/tests/envelope.rs
index 1712a99b..80591e14 100644
--- a/crates/vectorcraft-format/tests/envelope.rs
+++ b/crates/vectorcraft-format/tests/envelope.rs
@@ -252,6 +252,49 @@ fn contents_read_the_document_images_and_profiles_without_the_preview_and_pdf()
     assert!(Contents::<Doc>::read(no_document).is_err());
 }
 
+#[test]
+fn contents_read_pdf_preference_while_skipping_the_payload() {
+    for (members, expected) in [
+        ("", false),
+        (r#", "pdf":null"#, false),
+        (r#", "pdf":{"data":"not base64"}"#, true),
+        (r#", "pdf":[1,2,3]"#, true),
+        (r#", "pdfCompatible":true"#, true),
+        (r#", "pdf":{}, "pdfCompatible":false"#, false),
+        (r#", "pdfCompatible":false, "pdf":{}"#, false),
+        (r#", "pdfCompatible":true, "pdfCompatible":null, "pdf":{}"#, true),
+        (r#", "pdf":{}, "pdf":null"#, false),
+        (r#", "pdfCompatible":false, "pdfCompatible":true"#, true),
+        (r#", "unknown":{"pdf":{}}"#, false),
+    ] {
+        let json = format!(r#"{{"format":"vectorcraft","version":4,"document":{{"layers":[]}}{members}}}"#);
+        let (contents, compatible) = Contents::<Doc>::read_with_pdf_preference(json.as_bytes()).unwrap();
+        assert_eq!(compatible, expected, "{members}");
+        assert_eq!(contents, Contents::<Doc>::read(json.as_bytes()).unwrap());
+    }
+    let array = br#"["drawcraft",1,{"layers":[]}]"#;
+    assert!(!Contents::<Doc>::read_with_pdf_preference(array).unwrap().1);
+    let mut file = File::new(doc());
+    file.pdf = Some(Image::inline("application/pdf", &vec![7; 128 << 10]));
+    assert!(Contents::<Doc>::read_with_pdf_preference(&serde_json::to_vec(&file).unwrap()).unwrap().1);
+}
+
+#[test]
+fn pdf_preference_read_is_opt_in_and_preserves_envelope_validation() {
+    let invalid = br#"{"format":"vectorcraft","version":4,"document":{"layers":[]},"pdfCompatible":"invalid"}"#;
+    assert!(Contents::<Doc>::read(invalid).is_ok());
+    assert!(File::<Doc>::read(invalid).is_ok());
+    assert!(Contents::<Doc>::read_with_pdf_preference(invalid).is_err());
+    for json in [
+        br#"{"format":"other","version":4,"document":{"layers":[]}}"#.as_slice(),
+        br#"{"format":"vectorcraft","version":999,"document":{"layers":[]}}"#.as_slice(),
+        br#"{"format":"vectorcraft","version":4}"#.as_slice(),
+        br#"{"format":"vectorcraft","version":4,"version":4,"document":{"layers":[]}}"#.as_slice(),
+    ] {
+        assert_eq!(Contents::<Doc>::read(json).unwrap_err().to_string(), Contents::<Doc>::read_with_pdf_preference(json).unwrap_err().to_string());
+    }
+}
+
 #[test]
 fn reading_refuses_another_format_and_a_newer_version() {
     let newer = br#"{"format":"vectorcraft","version":5,"document":0}"#;