diff --git a/doc.go b/doc.go
index ddae8ae..dd12120 100644
--- a/doc.go
+++ b/doc.go
@@ -27,6 +27,10 @@ type Doc struct {
 	flatten      bool
 	dropAnnots   bool
 	dropOutlines bool
+	// outline, when set, is written instead of carrying the sources' own
+	// bookmarks over: a document assembled rather than merged has an outline
+	// of its caller's rather than of anybody else's.
+	outline []Bookmark
 
 	// How the file is written: packed into compressed object streams, and
 	// protected or not.
diff --git a/outlines.go b/outlines.go
index e7b1aa0..30e774a 100644
--- a/outlines.go
+++ b/outlines.go
@@ -21,17 +21,43 @@ type outlineItem struct {
 // that loses every bookmark is a poor merge.
 func (d *Doc) DropOutlines() { d.dropOutlines = true }
 
-// writeOutlines carries the bookmarks of every source document over, in the
-// order the documents first contribute a page, dropping whatever pointed at a
-// page that is no longer here.
-func (d *Doc) writeOutlines(w *reader.Writer, where destinations) reader.Object {
+// A Bookmark is an entry of an outline written from scratch: what it says, the
+// page of this document it points at counting from one, and whatever sits
+// under it.
+//
+// It is what a document assembled rather than merged carries — a shared
+// edit, a report built out of pieces — where there is no source outline to
+// carry over because the outline is the caller's own.
+type Bookmark struct {
+	Title    string
+	Page     int
+	Children []Bookmark
+}
+
+// SetOutline writes these bookmarks rather than carrying over the ones the
+// sources had. An entry pointing at a page this document has not got is left
+// out, and so is everything under it: a heading whose section has gone is not
+// a heading any more.
+//
+// Passing nothing puts the sources' own bookmarks back.
+func (d *Doc) SetOutline(marks []Bookmark) { d.outline = marks }
+
+// writeOutlines writes the bookmarks the caller set, or carries over those of
+// every source document, in the order the documents first contribute a page,
+// dropping whatever pointed at a page that is no longer here.
+func (d *Doc) writeOutlines(w *reader.Writer, where destinations, refs []reader.Ref) reader.Object {
 	if d.dropOutlines {
 		return nil
 	}
 	var items []outlineItem
-	budget := maxOutlineItems
-	for _, src := range d.sources() {
-		items = append(items, d.readOutlines(w, src, where, &budget)...)
+	if len(d.outline) > 0 {
+		budget := maxOutlineItems
+		items = d.buildOutline(refs, d.outline, 0, &budget)
+	} else {
+		budget := maxOutlineItems
+		for _, src := range d.sources() {
+			items = append(items, d.readOutlines(w, src, where, &budget)...)
+		}
 	}
 	if len(items) == 0 {
 		return nil
@@ -62,6 +88,30 @@ func (d *Doc) sources() []*reader.Document {
 	return out
 }
 
+// buildOutline turns the caller's bookmarks into the ones a file carries,
+// dropping any that point nowhere in this document.
+func (d *Doc) buildOutline(refs []reader.Ref, marks []Bookmark, depth int, budget *int) []outlineItem {
+	if depth > maxOutlineDepth {
+		return nil
+	}
+	var out []outlineItem
+	for _, m := range marks {
+		if *budget <= 0 {
+			return out
+		}
+		if m.Page < 1 || m.Page > len(refs) {
+			continue
+		}
+		*budget--
+		out = append(out, outlineItem{
+			title:    []byte(m.Title),
+			dest:     reader.Array{refs[m.Page-1], reader.Name("Fit")},
+			children: d.buildOutline(refs, m.Children, depth+1, budget),
+		})
+	}
+	return out
+}
+
 // readOutlines reads one document's bookmarks.
 func (d *Doc) readOutlines(w *reader.Writer, src *reader.Document, where destinations, budget *int) []outlineItem {
 	cat, _ := src.Catalog()
diff --git a/outlines_test.go b/outlines_test.go
index 4a4aa2d..1785b35 100644
--- a/outlines_test.go
+++ b/outlines_test.go
@@ -163,3 +163,86 @@ func TestBookmarksOfMadePagesAreNone(t *testing.T) {
 		t.Errorf("bookmarks = %v", got)
 	}
 }
+
+func TestAnOutlineWrittenFromScratch(t *testing.T) {
+	// A document assembled rather than merged has an outline of its caller's:
+	// there is no source outline to carry over.
+	d, err := Open(simple(t, 5))
+	if err != nil {
+		t.Fatal(err)
+	}
+	d.SetOutline([]Bookmark{
+		{Title: "One", Page: 1, Children: []Bookmark{
+			{Title: "One and a half", Page: 2},
+		}},
+		{Title: "Three", Page: 3},
+		{Title: "Nowhere", Page: 99},     // past the end
+		{Title: "Also nowhere", Page: 0}, // not a page
+		{Title: "Gone", Page: 42, Children: []Bookmark{{Title: "Under", Page: 1}}},
+	})
+	back, _ := writeAndOpen(t, d)
+	titles := outlineTitles(t, back)
+	want := []string{"One", "One and a half", "Three"}
+	if !reflect.DeepEqual(titles, want) {
+		t.Errorf("the outline says %v, want %v", titles, want)
+	}
+}
+
+func TestAnOutlineSetAndThenTakenBack(t *testing.T) {
+	// Passing nothing puts the sources' own bookmarks back, and asking for
+	// none at all still wins.
+	f := richPDF(t, 3)
+	d, err := Open(f.bytes)
+	if err != nil {
+		t.Fatal(err)
+	}
+	d.SetOutline([]Bookmark{{Title: "Mine", Page: 1}})
+	back, _ := writeAndOpen(t, d)
+	if titles := outlineTitles(t, back); len(titles) != 1 || titles[0] != "Mine" {
+		t.Errorf("the outline says %v", titles)
+	}
+
+	d, _ = Open(f.bytes)
+	d.SetOutline(nil)
+	back, _ = writeAndOpen(t, d)
+	if titles := outlineTitles(t, back); len(titles) == 0 {
+		t.Error("the source's own bookmarks were not put back")
+	}
+
+	d, _ = Open(f.bytes)
+	d.SetOutline([]Bookmark{{Title: "Mine", Page: 1}})
+	d.DropOutlines()
+	back, _ = writeAndOpen(t, d)
+	if titles := outlineTitles(t, back); len(titles) != 0 {
+		t.Errorf("bookmarks were written after being dropped: %v", titles)
+	}
+}
+
+func TestAnOutlineDeeperThanAnyoneNeeds(t *testing.T) {
+	// A tree deeper than the format is read to, and one wider than it is
+	// carried to, are both cut off rather than followed.
+	deep := Bookmark{Title: "top", Page: 1}
+	at := &deep
+	for i := 0; i < maxOutlineDepth+5; i++ {
+		at.Children = []Bookmark{{Title: "under", Page: 1}}
+		at = &at.Children[0]
+	}
+	d, err := Open(simple(t, 2))
+	if err != nil {
+		t.Fatal(err)
+	}
+	d.SetOutline([]Bookmark{deep})
+	if _, err := d.Bytes(); err != nil {
+		t.Fatal(err)
+	}
+
+	wide := make([]Bookmark, maxOutlineItems+10)
+	for i := range wide {
+		wide[i] = Bookmark{Title: "one", Page: 1}
+	}
+	d, _ = Open(simple(t, 2))
+	d.SetOutline(wide)
+	if _, err := d.Bytes(); err != nil {
+		t.Fatal(err)
+	}
+}
diff --git a/write.go b/write.go
index 5c53579..62132a5 100644
--- a/write.go
+++ b/write.go
@@ -65,7 +65,7 @@ func (d *Doc) Bytes() ([]byte, error) {
 	})
 
 	catalog := reader.Dict{"Type": reader.Name("Catalog"), "Pages": pagesRef}
-	if outlines := d.writeOutlines(w, where); outlines != nil {
+	if outlines := d.writeOutlines(w, where, refs); outlines != nil {
 		catalog["Outlines"] = outlines
 	}
 	trailer := reader.Dict{"Root": w.Add(catalog)}