Opening and Saving PDFs

UWP introduced new rules around file access permissions, and if you’re not familiar with them, it’s worth reading about them here.

Microsoft also has several guide articles that cover topics such as working with file pickers, tracking recently used files, and much more.

Opening PDFs

UWP represents files with the StorageFile class. You can use a file picker to present a UI to the user. This can be used for locating and retrieving a StorageFile for a PDF the user wishes to open.

The following example code demonstrates how to show the file picker and open a selected PDF:

// Open a picker so the user can choose a PDF.
var picker = new FileOpenPicker
    ViewMode = PickerViewMode.Thumbnail,
    SuggestedStartLocation = PickerLocationId.DocumentsLibrary

var file = await picker.PickSingleFileAsync();
if (file == null) return;

// Open and display the PDF in the PSPDFKit `PdfView`.
var documentSource = DocumentSource.CreateFromStorageFile(file);
await PdfView.Controller.ShowDocumentAsync(documentSource);

You can also open a file from a buffer:

// Get a buffer containing a PDF from somewhere, e.g. from a `StorageFile`.
var buffer = await FileIO.ReadBufferAsync(file);

var documentSource = DocumentSource.CreateFromBuffer(buffer);
await PdfView.Controller.ShowDocumentAsync(documentSource);

Opening Password-Protected PDFs

When opening password-protected PDFs, PSPDFKit will prompt your user with a password dialog, asking to unlock the PDF. If you want to programmatically supply a password instead, you can use the Password property of DocumentSource:

DocumentSource documentSource = ...

// Set the password in the document source.
documentSource.Password = "document-password";

await PDFView.Controller.ShowDocumentAsync(documentSource);

Handling Password Events

If you want to asynchronously provide the password whenever encountering a locked PDF, or if you want to implement your own password dialog, PDFView.Controller exposes the OnRequestPassword event, which is triggered whenever a password-protected PDF is opened without the correct password:

public async void OpenPDF(DocumentSource source)
    // Register the event handler that will asynchronously provide
    // the password for opening the encrypted PDF.
    PDFView.Controller.OnRequestPassword += Controller_OnRequestPassword;
    await PDFView.Controller.ShowDocumentAsync(documentSource);

/// <summary>
/// Event handler that is called every time PSPDFKit encounters a password-protected PDF.
/// </summary>
private async void Controller_OnRequestPassword(Controller sender, PasswordEventArgs args)
    // It is essential that we call `Complete()` on the `Deferral` at the end.
    var deferral = args.Deferral;

        // This can be synchronous or asynchronous (e.g. a user-facing dialog).
        var password = await GetPassword();
        args.Response = new PasswordRequestResponse(success: true, password: password, mayTryAgain: true);

Look at our PasswordDialogViewModel example inside the UWP catalog to see an example of this API in action.

Saving PDFs

In our API, the word export is synonymous with save. You have the choice to export from a Document to a StorageFile or a DataWriter:

// Export to a `StorageFile`.
await pdfView.Document.ExportAsync(storageFile);

// Export to an `InMemoryRandomAccessStream` via a `DataWriter`.
using (var inMemoryStream = new InMemoryRandomAccessStream())
using (var dataWriter = new DataWriter(inMemoryStream))
    await pdfView.Document.ExportToDataWriterAsync(dataWriter);

    // Here, the in-memory stream will contain the exported PDF.

Here is one way to save the currently open document to the file it was opened from:

// Get the `StorageFile`.
var file = pdfView.Controller?.GetPdfDocument()?.DocumentSource.GetFile();
if (file != null)
  // Save it.
  await pdfView.Document.ExportAsync(file);

Note that the PdfView supports automatically saving changes. See the related guide for details.

Incremental Saving

By default, PSPDFKit saves to files incrementally. This is a feature of PDF and means that when saving, the initial content of the original document is not altered and all changes are appended to the file. This can result in a significantly faster save when working with a large file, as changes are typically quite small.

However, you should bear in mind that since the changes are always appended, the file will constantly increase in size with every save, regardless of the changes being made. Since this is sometimes undesirable, you can specify that the PDF should be completely rewritten upon saving.

Here are some examples of saving incrementally:

// Save incrementally by default.
await pdfView.Document.ExportAsync(file);

// Explicitly save incrementally.
var exportOptions = new DocumentExportOptions{ Incremental = true };
await pdfView.Document.ExportAsync(file, exportOptions);

Here is how to rewrite the PDF when saving:

// Set `Incremental` to `false` to rewrite the document.
var exportOptions = new DocumentExportOptions{ Incremental = false };
await pdfView.Document.ExportAsync(file, exportOptions);

Note that you can also export a PDF with flattened annotations. However, flattening requires a full rewrite of the document, so the Incremental property of DocumentExportOptions is ignored if Flatten is set to true.