[Web] Signature appearance on page.Annots not visible in SfPdfViewer (pdf.js annotationMode=DISABLE)

[rontgenricohermoso-mobbiz]

Bug description

On Flutter Web, SfPdfViewer does not show a signature stamp that is clearly present when the same PDF is downloaded and opened in Chrome’s native PDF viewer (or Preview / Adobe).

Sample file (attached):
Alliances - Mobbiz - Partnership Agreement - Indra_15JUNE2026v.254 (1).pdf

• Page 5 – Devops Outsourcing Inc.: handwritten ink signature is visible in SfPdfViewer (drawn into page content).
• Page 5 – Indra Philippines Inc.: digital-style stamp (“Digitally signed by Diego Antonio P. Castillejo…”) is missing in SfPdfViewer, but visible after Download → open in Chrome.

This is related in theme to #2506, but our case is Web, and upgrading the Syncfusion package alone did not restore the Indra stamp in the built-in preview.

PDF structure (from inspection of the attached file):

• Page 5 has a /Subtype /Widget + /FT /Sig annotation named Signature2 with an /AP appearance stream that contains the “Digitally signed by…” text.
• AcroForm.Fields is empty; there is no /V cryptographic signature dictionary on that widget (Apple Preview / Quartz-style appearance).
• Producer: macOS Quartz PDFContext; Creator: Microsoft Word.

Why it fails with current Syncfusion Web path:

• syncfusion_pdfviewer_web renders via pdf.js with annotationMode = 0 (DISABLE) → Annot appearances are not painted.
• _renderDigitalSignatures() only flattens fields in document.form.fields when signature != null → this Annot-only stamp is never flattened into page content.

Expected Behavior

• SfPdfViewer on Web should show the Indra signature appearance on page 5 the same way Chrome does when opening the attached PDF.

Alliances - Mobbiz - Partnership Agreement - Indra_15JUNE2026v.254 (1).pdf

Actual Behavior

• In-app preview: Indra stamp area blank; Devops ink signature still shows.
• Download → Chrome: both signatures / stamp visible.

Steps to reproduce

1. Create a Flutter Web app with syncfusion_flutter_pdfviewer 32.2.9 (and required pdf.js setup in web/index.html).
2. Load the attached PDF with SfPdfViewer.memory (or .file).
3. Go to page 5.
4. Observe Indra block has no digital stamp.
5. Open the same file in Chrome’s PDF viewer → stamp is present.

Code sample

@override Widget build(BuildContext context) { return Scaffold( body: SfPdfViewer.memory( pdfBytes, // attached partnership agreement PDF onDocumentLoadFailed: (PdfDocumentLoadFailedDetails details) { print('Load Failed: ${details.description}'); }, ), ); }

Workaround Used
Temporary local override of syncfusion_pdfviewer_web: set pdf.js annotationMode from 0 to 1 (ENABLE) in the page/tile render settings. With that change, the Indra stamp appears in preview. We consider this temporary until Syncfusion provides an official fix/API.

`// syncfusion_pdfviewer_web – render settings
..annotationMode = 1; // stock package uses 0 (DISABLE)

Alliances - Mobbiz - Partnership Agreement - Indra_15JUNE2026v.254 (1).pdf

`

Screenshots or Video

BAD:

GOOD:

Alliances - Mobbiz - Partnership Agreement - Indra_15JUNE2026v.254 (1).pdf

Stack Traces

No stack trace — silent visual rendering issue, not a crash. See description above.

On which target platforms have you observed this bug?

Web

Flutter Doctor output

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 3.44.8, on macOS 15.6 24G84 darwin-arm64, locale en)
[✓] Android toolchain - develop for Android devices (Android SDK version 36.0.0)
[✓] Xcode - develop for iOS and macOS (Xcode 26.3)
[✓] Chrome - develop for the web
[✓] Connected device (4 available)
[✓] Network resources

• No issues found!

[AbinayaSF4962]

Hi @rontgenricohermoso-mobbiz ,

After analyzing the shared document, we found that the issue is specific to the PDF structure. The signature appearance on page 5 is stored as a signature widget annotation, but it is not properly mapped in the document's /AcroForm structure. As a result, the signature is not recognized as a standard PDF form field by the viewer.
Therefore, this behavior is related to the way the PDF was generated rather than an issue with the Syncfusion PDF Viewer itself.

Regards,
Abinaya E