fix: normalize and flatten annotations

packages/lib/server-only/pdf/flatten-annotations.ts

@@ -0,0 +1,63 @@
+import { PDFAnnotation, PDFRef } from 'pdf-lib';
+import {
+  PDFDict,
+  type PDFDocument,
+  PDFName,
+  drawObject,
+  popGraphicsState,
+  pushGraphicsState,
+  rotateInPlace,
+  translate,
+} from 'pdf-lib';
+
+export const flattenAnnotations = (document: PDFDocument) => {
+  const pages = document.getPages();
+
+  for (const page of pages) {
+    const annotations = page.node.Annots()?.asArray() ?? [];
+
+    annotations.forEach((annotation) => {
+      if (!(annotation instanceof PDFRef)) {
+        return;
+      }
+
+      const actualAnnotation = page.node.context.lookup(annotation);
+
+      if (!(actualAnnotation instanceof PDFDict)) {
+        return;
+      }
+
+      const pdfAnnot = PDFAnnotation.fromDict(actualAnnotation);
+
+      const appearance = pdfAnnot.ensureAP();
+
+      // Skip annotations without a normal appearance
+      if (!appearance.has(PDFName.of('N'))) {
+        return;
+      }
+
+      const normalAppearance = pdfAnnot.getNormalAppearance();
+      const rectangle = pdfAnnot.getRectangle();
+
+      if (!(normalAppearance instanceof PDFRef)) {
+        // Not sure how to get the reference to the normal appearance yet
+        // so we should skip this annotation for now
+        return;
+      }
+
+      const xobj = page.node.newXObject('FlatAnnot', normalAppearance);
+
+      const operators = [
+        pushGraphicsState(),
+        translate(rectangle.x, rectangle.y),
+        ...rotateInPlace({ ...rectangle, rotation: 0 }),
+        drawObject(xobj),
+        popGraphicsState(),
+      ].filter((op) => !!op);
+
+      page.pushOperators(...operators);
+
+      page.node.removeAnnot(annotation);
+    });
+  }
+};

packages/lib/server-only/pdf/normalize-signature-appearances.ts

@@ -0,0 +1,26 @@
+import type { PDFDocument } from 'pdf-lib';
+import { PDFSignature, rectangle } from 'pdf-lib';
+
+export const normalizeSignatureAppearances = (document: PDFDocument) => {
+  const form = document.getForm();
+
+  for (const field of form.getFields()) {
+    if (field instanceof PDFSignature) {
+      field.acroField.getWidgets().forEach((widget) => {
+        widget.ensureAP();
+
+        try {
+          widget.getNormalAppearance();
+        } catch {
+          const { context } = widget.dict;
+
+          const xobj = context.formXObject([rectangle(0, 0, 0, 0)]);
+
+          const streamRef = context.register(xobj);
+
+          widget.setNormalAppearance(streamRef);
+        }
+      });
+    }
+  }
+};