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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 handle the prompt and retry flow in your application code.

Recommended workflow (LoadImage() / LoadImageEx())

  1. Call LoadImage() or LoadImageEx().
  2. In the failure callback, treat the error as “password required” only when either condition is true:
    • (errorCode is -1119 and errorString contains
      "Failed to read the PDF file because it's encrypted and the correct password is not provided.")
    • OR errorCode is -1120.
  3. Prompt the user for a password.
  4. Set the password via SetReaderOptions().
  5. Retry loading the same PDF.

Helper function for password-required errors

Use this helper in both API-based loading and drag-and-drop handling:

function isPasswordRequired(errorCode, errorString) {
    return (
        (errorCode === -1119 &&
            (errorString || "").includes(
                "Failed to read the PDF file because it's encrypted and the correct password is not provided.",
            )) ||
        errorCode === -1120
    );
}

LoadImage() / LoadImageEx() example

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 (!isPasswordRequired(errorCode, errorString)) {
                console.error(errorCode, errorString);
                return;
            }

            var userPassword = window.prompt(
                "This PDF is password-protected. Please enter the password:",
                "",
            );
            if (!userPassword) return;

            loadProtectedPdf(path, userPassword);
        },
    );
}

Drag-and-drop workflow (OnPostLoad)

Use OnPostLoad and check DWTObject.ErrorCode / DWTObject.ErrorString.

DWTObject.RegisterEvent("OnPostLoad", function (path, name, type) {
    if (!isPasswordRequired(DWTObject.ErrorCode, DWTObject.ErrorString)) return;

    var userPassword = window.prompt(
        "This PDF is password-protected. Please enter the password:",
        "",
    );
    if (!userPassword) return;

    DWTObject.Addon.PDF.SetReaderOptions({ password: userPassword });

    if (!path) {
        alert("Password saved. Please drag and drop the file again.");
        return;
    }

    var fullPath = path + "\\" + name;
    loadProtectedPdf(fullPath, userPassword);
});

-1119 can represent multiple PDF load issues, so do not use it alone. Starting in Dynamic Web TWAIN 19.4, encrypted-PDF load failures will use -1120.

In OnPostLoad, path is empty for drag-and-drop files, so the code cannot directly retry with a file path. In this case, prompt for password, save it with SetReaderOptions(), and ask the user to drag and drop the file again.

Original post creation date: Apr 09, 2026

Last modified date: Apr 09, 2026