docs(faq): add password-protected PDF loading guidance

Author: lyzhang0113

_articles/faq/index.md

@@ -142,6 +142,7 @@ description: Dynamic Web TWAIN SDK Documentation FAQ
 8.  [How can I separate my documents automatically by barcode?](/_articles/faq/separate-documents-by-barcode.md)
 9.  [Is there any way to speed up the barcode reading process?](/_articles/faq/speed-up-barcode-reading-process.md)
 10.  [What types of webcams does the Webcam Capture addon support](/_articles/faq/webcam-supported-by-webcam-capture-addon.md)
+11.  [How can I prompt users for a password when loading a password-protected PDF?](/_articles/faq/prompt-password-for-protected-pdf.md)
 
 ## Project Deployment and End-user Installation
 
@@ -228,4 +229,4 @@ description: Dynamic Web TWAIN SDK Documentation FAQ
 
 ## Annotation
 
-1.  [How can I add annotations to an image and then save/upload it?](/_articles/faq/dwt-with-annotation.md)
+1.  [How can I add annotations to an image and then save/upload it?](/_articles/faq/dwt-with-annotation.md)

_articles/faq/prompt-password-for-protected-pdf.md

@@ -0,0 +1,71 @@
+---
+layout: default-layout
+noTitleIndex: true
+needAutoGenerateSidebar: true
+title: How can I prompt users for a password when loading a password-protected PDF?
+keywords: Dynamic Web TWAIN, Addon, PDF, password, encrypted, LoadImageEx, OnPostLoad
+breadcrumbText: How can I prompt users for a password when loading a password-protected PDF?
+description: How can I prompt users for a password when loading a password-protected PDF?
+date: 2026-04-09 10:00:00 +0800
+last_modified: 2026-04-09 10:00:00 +0800
+---
+
+# Addon
+
+## How can I prompt users for a password when loading a password-protected PDF?
+
+Dynamic Web TWAIN does not provide a built-in password prompt UI for encrypted PDFs.  
+You need to implement your own prompt flow in application code.
+
+### Recommended flow for `LoadImage()` / `LoadImageEx()`
+
+1. Call [`LoadImage()`](/_articles/info/api/WebTwain_IO.md#loadimage) or [`LoadImageEx()`](/_articles/info/api/WebTwain_IO.md#loadimageex).
+2. In the failure callback, check whether `errorCode` is `-1119`.
+3. Prompt the user for a password.
+4. Call [`SetReaderOptions()`](/_articles/info/api/Addon_PDF.md#setreaderoptions) with that password.
+5. Retry loading the same PDF.
+
+```javascript
+function loadProtectedPdf(path, password) {
+    DWTObject.Addon.PDF.SetReaderOptions({ password: password || "" });
+    DWTObject.LoadImageEx(
+        path,
+        Dynamsoft.DWT.EnumDWT_ImageType.IT_PDF,
+        function () {
+            console.log("PDF loaded successfully.");
+        },
+        function (errorCode, errorString) {
+            if (errorCode !== -1119) {
+                console.error(errorCode, errorString);
+                return;
+            }
+
+            var userPassword = window.prompt(
+                "This PDF is password-protected. Please enter the password:",
+                "",
+            );
+            if (!userPassword) return;
+
+            loadProtectedPdf(path, userPassword);
+        },
+    );
+}
+```
+
+### For drag-and-drop files
+
+You can detect load failures in [`OnPostLoad`](/_articles/info/api/WebTwain_IO.md#onpostload) by checking `DWTObject.ErrorCode` and `DWTObject.ErrorString`.
+
+```javascript
+DWTObject.RegisterEvent("OnPostLoad", function (path, name, type) {
+    if (DWTObject.ErrorCode === -1119) {
+        console.log(DWTObject.ErrorString);
+        // Add your own password prompt flow here.
+    }
+});
+```
+
+> [!NOTE]
+> In `OnPostLoad`, `path` is empty for drag-and-drop files.
+> If you need a retry flow after entering a password, prompt the user to select the file again
+> (for example, by using [`ShowFileDialog()`](/_articles/info/api/WebTwain_IO.md#showfiledialog) + [`LoadImageEx()`](/_articles/info/api/WebTwain_IO.md#loadimageex)).