Rewrite an unsigned file in full when saving after deleting pages (#3407)

crates/engine/src/lib.rs

@@ -3945,6 +3945,11 @@ impl Session {
         // Signed documents are only ever saved incrementally: an edit that needs a full rewrite
         // (applying redactions, changing security, sanitizing) would invalidate the signatures.
         // So does any edit to a file rebuilt from object headers: it has no chain to append to.
+        // Deleted pages are freed, but an incremental save keeps them (and their text) in the
+        // earlier revision and the file does not shrink (#3407): rewrite an unsigned file in full.
+        if !signed && matches!(edit, Edit::DeletePages { .. }) {
+            next.require_full_save();
+        }
         let rewrites = |c: &pdfcraft_cos::Document| c.full_save_required() || c.encryption_changed();
         if signed && ((rewrites(&next) && !rewrites(&editor.cos)) || (next.is_modified() && next.revisions().is_empty())) {
             return Err(EditError::SignedRewrite(edit.label().to_string()));