diff --git a/crates/engine/src/fill_sign.rs b/crates/engine/src/fill_sign.rs
new file mode 100644
index 000000000..08739addf
--- /dev/null
+++ b/crates/engine/src/fill_sign.rs
@@ -0,0 +1,47 @@
+//! Fill & Sign geometry: typed signatures, and boxes placed as a turned page displays them.
+
+use crate::{Shape, script_outline, signature_image};
+
+/// Fill & Sign: `text` in the script font as a typed signature, its left edge at `at` (user
+/// space, vertically centred) and `height` points tall. `None` for text with no outlines.
+///
+/// Left, centred and upright are as displayed on a page turned by `rotation` (its `/Rotate`):
+/// the box runs along the displayed axes, like an image signature's
+/// ([`SignatureImage::rect`]), and the outlines are turned back so the name reads across.
+pub fn typed_signature_shape(at: [f64; 2], text: &str, height: f64, rotation: i64) -> Option<Shape> {
+    let o = script_outline(text);
+    let [left, bottom, right, top] = o.bounds();
+    let span = (top - bottom).max(0.1);
+    let width = right - left;
+    if o.contours.is_empty() || o.width <= 0.0 || !(width > 0.0 && height > 0.0) {
+        return None;
+    }
+    let k = height / span;
+    let rect = signature_image::upright_box(rotation, at, width * k, height)?;
+    // Displayed right and up as user-space unit vectors: a point at (nx, ny) of the displayed box
+    // is at this fraction of the user-space box. Exact for an unturned page.
+    let [a, b, c, d, ..] = pdfcraft_model::view_matrix_for(rotation, [0.0; 4]);
+    let to_user = |nx: f64, ny: f64| [a * nx + c * ny + (-a).max(0.0) + (-c).max(0.0), b * nx + d * ny + (-b).max(0.0) + (-d).max(0.0)];
+    let contours = o.contours.iter().map(|c| c.iter().map(|p| to_user((p[0] - left) / width, (p[1] - bottom) / span)).collect()).collect();
+    Some(Shape::TypedSignature { rect, contours })
+}
+
+/// `at` moved `right` and `up` points as displayed on a page turned by `rotation` (its `/Rotate`).
+pub fn displayed_offset(rotation: i64, at: [f64; 2], right: f64, up: f64) -> [f64; 2] {
+    let [a, b, c, d, ..] = pdfcraft_model::view_matrix_for(rotation, [0.0; 4]);
+    [at[0] + a * right + c * up, at[1] + b * right + d * up]
+}
+
+/// The user-space box `width` x `height` points as displayed on a page turned by `rotation`,
+/// with its displayed top-left corner at `at`: where typed text and text boxes go. `None` for a
+/// non-finite point.
+pub fn text_box_at(rotation: i64, at: [f64; 2], width: f64, height: f64) -> Option<[f64; 4]> {
+    signature_image::upright_box(rotation, displayed_offset(rotation, at, 0.0, -height / 2.0), width, height)
+}
+
+/// `text` in the script font as the graphic of a visible digital signature, as Fill & Sign types
+/// it. `None` for text with no outlines.
+pub fn typed_signature_graphic(text: &str) -> Option<pdfcraft_sign::Graphic> {
+    let o = script_outline(text);
+    o.contours.iter().any(|c| c.len() > 2).then_some(pdfcraft_sign::Graphic::Outlines(o.contours))
+}
diff --git a/crates/engine/src/lib.rs b/crates/engine/src/lib.rs
index ea9c267ae..25428ebf6 100644
--- a/crates/engine/src/lib.rs
+++ b/crates/engine/src/lib.rs
@@ -30,6 +30,7 @@ mod edit;
 mod error;
 pub mod export;
 pub mod field_table;
+mod fill_sign;
 mod history;
 pub mod js;
 mod layers;
@@ -84,49 +85,6 @@ pub enum ImageEdit {
     Delete,
 }
 
-/// Fill & Sign: `text` in the script font as a typed signature, its left edge at `at` (user
-/// space, vertically centred) and `height` points tall. `None` for text with no outlines.
-///
-/// Left, centred and upright are as displayed on a page turned by `rotation` (its `/Rotate`):
-/// the box runs along the displayed axes, like an image signature's
-/// ([`SignatureImage::rect`]), and the outlines are turned back so the name reads across.
-pub fn typed_signature_shape(at: [f64; 2], text: &str, height: f64, rotation: i64) -> Option<Shape> {
-    let o = script_outline(text);
-    let [left, bottom, right, top] = o.bounds();
-    let span = (top - bottom).max(0.1);
-    let width = right - left;
-    if o.contours.is_empty() || o.width <= 0.0 || !(width > 0.0 && height > 0.0) {
-        return None;
-    }
-    let k = height / span;
-    let rect = signature_image::upright_box(rotation, at, width * k, height)?;
-    // Displayed right and up as user-space unit vectors: a point at (nx, ny) of the displayed box
-    // is at this fraction of the user-space box. Exact for an unturned page.
-    let [a, b, c, d, ..] = pdfcraft_model::view_matrix_for(rotation, [0.0; 4]);
-    let to_user = |nx: f64, ny: f64| [a * nx + c * ny + (-a).max(0.0) + (-c).max(0.0), b * nx + d * ny + (-b).max(0.0) + (-d).max(0.0)];
-    let contours = o.contours.iter().map(|c| c.iter().map(|p| to_user((p[0] - left) / width, (p[1] - bottom) / span)).collect()).collect();
-    Some(Shape::TypedSignature { rect, contours })
-}
-/// `at` moved `right` and `up` points as displayed on a page turned by `rotation` (its `/Rotate`).
-pub fn displayed_offset(rotation: i64, at: [f64; 2], right: f64, up: f64) -> [f64; 2] {
-    let [a, b, c, d, ..] = pdfcraft_model::view_matrix_for(rotation, [0.0; 4]);
-    [at[0] + a * right + c * up, at[1] + b * right + d * up]
-}
-
-/// The user-space box `width` x `height` points as displayed on a page turned by `rotation`,
-/// with its displayed top-left corner at `at`: where typed text and text boxes go. `None` for a
-/// non-finite point.
-pub fn text_box_at(rotation: i64, at: [f64; 2], width: f64, height: f64) -> Option<[f64; 4]> {
-    signature_image::upright_box(rotation, displayed_offset(rotation, at, 0.0, -height / 2.0), width, height)
-}
-
-/// `text` in the script font as the graphic of a visible digital signature, as Fill & Sign types
-/// it. `None` for text with no outlines.
-pub fn typed_signature_graphic(text: &str) -> Option<pdfcraft_sign::Graphic> {
-    let o = script_outline(text);
-    o.contours.iter().any(|c| c.len() > 2).then_some(pdfcraft_sign::Graphic::Outlines(o.contours))
-}
-
 pub use links::{
     MAX_REMOTE_DOCUMENT_BYTES, RemoteDocumentPathError, read_remote_document, remote_document_path_is_absolute, resolve_remote_document_path,
 };
@@ -200,6 +158,7 @@ pub use document::{Document, TextNotice, display_bytes_for, render_password_for}
 use document::{display_bytes, info_fields, recovered_render_password, same_pages, shown_under_redactions, undrawn_notices};
 pub use edit::{BATCH_LABELS, EDIT_LABELS, Edit};
 pub use error::{EditError, SourceProblem};
+pub use fill_sign::{displayed_offset, text_box_at, typed_signature_graphic, typed_signature_shape};
 pub use history::Label;
 use layers::{apply_layer_state, set_default_layer_state, use_layer_choices};
 pub use open::{OpenContext, PreparedDocument};