diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4d073a45b..dae2346c1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,10 @@ The release run heads these entries with the version and opens a fresh
 
 ## Unreleased
 
+- The pdf view reports the pending annotation count on
+  `odr.onAnnotationChange({count})`, and `odr.annotation.press` and `recolor`
+  do what a tool button does.
+
 - The wasm `Document.edit`, `save`, `isEditable` and `isSavable` work for a
   plain text file, which saves as UTF-8.
 
diff --git a/docs/design/editing.md b/docs/design/editing.md
index b28ee3acd..664e02e49 100644
--- a/docs/design/editing.md
+++ b/docs/design/editing.md
@@ -483,4 +483,6 @@ version drifting until a new check page caught it.
   `odr.annotation` is its own API and `PdfFile::annotate` its own write path.
   It is a different gesture from editing text, so whether it should share the
   mode is a real question rather than an oversight
-  ([`txt-editing.md`](txt-editing.md) carries it too).
+  ([`txt-editing.md`](txt-editing.md) carries it too). It reports on a
+  callback of its own, `odr.onAnnotationChange`, and a pdf page does not
+  carry `editing.js`.
diff --git a/src/odr/internal/html/frontend/pdf-annotation.js b/src/odr/internal/html/frontend/pdf-annotation.js
index 555953b14..1bb0a3143 100644
--- a/src/odr/internal/html/frontend/pdf-annotation.js
+++ b/src/odr/internal/html/frontend/pdf-annotation.js
@@ -18,6 +18,21 @@
     overscrollBehavior: "contain",
   };
 
+  /// Raised as the pending count changes; a stroke counts once it ends.
+  odr.onAnnotationChange = function () {};
+
+  var reported = 0;
+
+  function changed() {
+    if (pending.length === reported) {
+      return;
+    }
+    reported = pending.length;
+    if (typeof odr.onAnnotationChange === "function") {
+      odr.onAnnotationChange({ count: pending.length });
+    }
+  }
+
   function pages() {
     return Array.prototype.slice.call(
       document.querySelectorAll("[data-odr-space]")
@@ -269,8 +284,8 @@
 
   /// One annotation per page the selection covers. `keep` holds the selection,
   /// which the automatic path cannot: the next `selectionchange` re-marks it.
-  function markSelection(keep) {
-    if (!tool || tool === "ink") {
+  function markSelection(type, rgb, keep) {
+    if (!type || type === "ink") {
       return false;
     }
     var byPage = selectionBoxes();
@@ -279,9 +294,9 @@
       pending.push({
         id: nextId++,
         page: +index,
-        type: tool,
+        type: type,
         boxes: byPage[index],
-        color: color.slice(),
+        color: rgb.slice(),
       });
       added = true;
     });
@@ -290,10 +305,41 @@
         window.getSelection().removeAllRanges();
       }
       redraw();
+      changed();
     }
     return added;
   }
 
+  function arm(value) {
+    tool = value || null;
+    pages().forEach(function (page) {
+      page.classList.toggle("an-draw", tool === "ink");
+    });
+    document.documentElement.classList.toggle("an-drawing", tool === "ink");
+  }
+
+  function rgbOf(value) {
+    return value.slice(0, 3).map(Number);
+  }
+
+  function applyStyle(style) {
+    if (style && style.color) {
+      color = rgbOf(style.color);
+    }
+    if (style && style.width !== undefined) {
+      width = Number(style.width);
+    }
+  }
+
+  /// Marks the selection once and disarms, if there is anything to mark.
+  function markOnce(type, style) {
+    var rgb = style && style.color ? rgbOf(style.color) : color;
+    if (!markSelection(type, rgb, false)) {
+      return false;
+    }
+    arm(null);
+    return true;
+  }
 
   var stroke = null;
   var strokeNode = null;
@@ -326,7 +372,7 @@
     }
     window.clearTimeout(settle);
     settle = window.setTimeout(function () {
-      markSelection(false);
+      markSelection(tool, color, false);
     }, 50);
   }
 
@@ -415,6 +461,7 @@
     stroke = null;
     strokeNode = null;
     strokePointer = null;
+    changed();
   }
 
   function applyOptions() {
@@ -433,19 +480,35 @@
 
   odr.annotation = {
     /// null, "highlight", "underline", "strikeOut", "squiggly" or "ink".
-    setTool: function (value) {
-      tool = value || null;
-      pages().forEach(function (page) {
-        page.classList.toggle("an-draw", tool === "ink");
-      });
-      document.documentElement.classList.toggle("an-drawing", tool === "ink");
-    },
+    setTool: arm,
     getTool: function () {
       return tool;
     },
+    /// A tool button: marks a selection once, else arms @p type or disarms
+    /// it. @p style is `{color, width}`. Answers the tool left armed.
+    press: function (type, style) {
+      if (markOnce(type, style)) {
+        return tool;
+      }
+      if (type && type === tool) {
+        arm(null);
+      } else {
+        applyStyle(style);
+        arm(type);
+      }
+      return tool;
+    },
+    /// Marks a selection once, as `press` does, else restyles @p type if it is
+    /// armed. Answers the tool left armed.
+    recolor: function (type, style) {
+      if (!markOnce(type, style) && type && type === tool) {
+        applyStyle(style);
+      }
+      return tool;
+    },
     /// DeviceRGB, each component in [0, 1].
     setColor: function (value) {
-      color = value.slice(0, 3).map(Number);
+      color = rgbOf(value);
     },
     setWidth: function (value) {
       width = Number(value);
@@ -470,7 +533,7 @@
     /// Marks the selection with the armed tool, and answers whether anything
     /// was added. The selection is left standing.
     mark: function () {
-      return markSelection(true);
+      return markSelection(tool, color, true);
     },
     /// What is pending, newest last. Geometry is in page-box points.
     list: function () {
@@ -481,14 +544,17 @@
         return a.id !== id;
       });
       redraw();
+      changed();
     },
     undo: function () {
       pending.pop();
       redraw();
+      changed();
     },
     clear: function () {
       pending = [];
       redraw();
+      changed();
     },
     /// The payload `PdfFile::annotate` takes, in pdf user space.
     getAnnotations: function () {
diff --git a/test/browser/annotation/tests.html b/test/browser/annotation/tests.html
index 09493478b..a194a3d53 100644
--- a/test/browser/annotation/tests.html
+++ b/test/browser/annotation/tests.html
@@ -59,6 +59,7 @@
     <span class="sr">Selectable text on page two</span>
   </div>
 </div>
+<p id="outside">Text on no page</p>
 
 <script src="checks.js"></script>
 <script src="pdf-annotation.js"></script>
@@ -347,6 +348,114 @@
 
     api.clear();
     api.setTool(null);
+
+    // --- the host hears of every change to what is pending ----------------
+    const heard = [];
+    window.odr.onAnnotationChange = (event) => heard.push(event.count);
+    api.setTool("highlight");
+    selectRun(0);
+    api.mark();
+    check("a mark is reported", heard.join() === "1", heard);
+    api.undo();
+    check("an undo is reported", heard.join() === "1,0", heard);
+    api.undo();
+    api.clear();
+    check("an undo or a clear that changes nothing is not", heard.length === 2, heard);
+
+    heard.length = 0;
+    api.setTool("ink");
+    document.dispatchEvent(new PointerEvent("pointerdown", at(100, 500)));
+    document.dispatchEvent(new PointerEvent("pointermove", at(140, 540)));
+    check("a stroke is not reported while it is drawn", heard.length === 0, heard);
+    document.dispatchEvent(new PointerEvent("pointerup", at(140, 540)));
+    check("but once it ends", heard.join() === "1", heard);
+    api.remove(api.list()[0].id);
+    check("a removal is reported", heard.join() === "1,0", heard);
+    api.setTool(null);
+
+    // --- a tool button: mark a standing selection, or arm and disarm ------
+    heard.length = 0;
+    selectRun(0);
+    check(
+      "a press over a selection arms nothing",
+      api.press("underline", { color: [0, 0, 1] }) === null
+    );
+    const pressed = payload().annotations;
+    check(
+      "and marks it once, in the colour pressed",
+      pressed.length === 1 &&
+        pressed[0].type === "underline" &&
+        pressed[0].color.join() === "0,0,1",
+      pressed
+    );
+    check("the selection goes with it", window.getSelection().isCollapsed);
+    check("the host hears of it", heard.join() === "1", heard);
+
+    check("a press with nothing selected arms", api.press("highlight") === "highlight");
+    check("a second press disarms", api.press("highlight") === null);
+    api.press("highlight", { color: [1, 0, 0] });
+    check("a press on another tool swaps", api.press("squiggly") === "squiggly");
+    check("null disarms", api.press(null) === null);
+    const outside = document.createRange();
+    outside.selectNodeContents(document.getElementById("outside"));
+    window.getSelection().removeAllRanges();
+    window.getSelection().addRange(outside);
+    check(
+      "a press over a selection on no page arms",
+      api.press("underline") === "underline" && api.list().length === 1,
+      api.list()
+    );
+    api.press(null);
+    selectRun(0);
+    check("the pen arms over a selection too", api.press("ink", { width: 4 }) === "ink");
+    check("it marks nothing", api.list().length === 1, api.list());
+    api.press(null);
+
+    // the selection a press clears must not come back as a second mark
+    api.clear();
+    api.setOptions({ markOnSelection: true });
+    selectRun(0);
+    api.press("strikeOut");
+    await new Promise((r) => setTimeout(r, 100));
+    check("with markOnSelection, still once", api.list().length === 1, api.list());
+    api.setOptions({ markOnSelection: false });
+
+    // --- a new colour marks a selection, or restyles the armed tool -------
+    api.clear();
+    selectRun(0);
+    check(
+      "recolor over a selection marks it once",
+      api.recolor("highlight", { color: [0, 1, 0] }) === null &&
+        api.list().length === 1 &&
+        api.list()[0].color.join() === "0,1,0",
+      api.list()
+    );
+    api.clear();
+    api.press("highlight", { color: [1, 1, 0] });
+    api.recolor("highlight", { color: [0, 1, 1] });
+    selectRun(0);
+    api.mark();
+    check(
+      "recolor restyles the armed tool",
+      api.list()[0].color.join() === "0,1,1",
+      api.list()[0].color
+    );
+    api.clear();
+    // mark() left it standing
+    window.getSelection().removeAllRanges();
+    api.recolor("underline", { color: [1, 0, 1] });
+    check("and arms nothing that was not armed", api.getTool() === "highlight");
+    selectRun(0);
+    api.mark();
+    check(
+      "nor restyles the armed one",
+      api.list()[0].color.join() === "0,1,1",
+      api.list()[0].color
+    );
+
+    window.odr.onAnnotationChange = () => {};
+    api.clear();
+    api.setTool(null);
   }
 
   run();