The character is visualized as '3'. The same issue is also reproducible when the content is copied from Adobe.

Loading document containing link with no destination leads to ArgumentNullException in PdfElementToFixedElementTranslator.CreateDestination method.

When importing a document with empty pages collection an ArgumentNullException: 'Value cannot be null.
Parameter name: page', is thrown, which leads to application crash.

Workaround: Import the document using the PdfProcessing library and add an empty page:

 

The CIDFont dictionary may contain an array, describing the widths of the glyphs. If the width has a negative value an ArgumentException: 'Width and Height must be non-negative.', is thrown when the document is imported in RadPdfViewer, which leads to application crash.

By specification, the InteractiveForm fields can have the same name if they are descendants of a common ancestor. Such fields are different representations of the same underlying field; they should differ only in properties that specify their visual appearance. When such a document is imported an ArgumentException: 'An item with the same key has already been added.' is thrown, which leads to non-editable fields in RadPdfViewer.

The EI keyword defines an operator for ending the image data. When the stream contains the same sequence, the parser treats that as an end of the image data. As a result, the image and the following content cannot be properly parsed and there is missing content when the document is visualized.

The offset of the CropBox is not respected and is always treated as 0.

Workaround: Import the document with PdfProcessing, change the CropBox offsets of the pages to 0, export the modified document and then import it in PdfViewer.

Telerik.Windows.Zip.InvalidDataException for unknown (0xAD) compression method is thrown for some object streams.

We should implement the logic for getting character codes from Unicode when using CFFFontSource.
Workaround: The font may be changed by creating a similar font with FontsRepository.TryCreateFont(...) method.

In the PDF document model, the Annotation appearances refer to an external resource using the Resources dictionary. When the Resources dictionary is defined as an Indirect Object an InvalidCastException: 'Unable to cast object of type 'Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Model.Types.PdfDictionary' to type 'Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Model.Elements.DocumentStructure.PdfResource'.', is thrown.

OverflowException is thrown while importing document using Helvetica font with custom encoding.

Text characters are missing when document is loaded in RadPdfViewer. When Fit to Page is used then numerous text characters vanish. They do not reappear when zooming back in.

When RadPdfViewer is in text selection mode and the user is trying to select a word by double-clicking on it, the last letter of the word is not selected when the word is followed by some symbols like '.', ':', '(', '...'

When using SaveAsCommandDescriptor of RadPdfViewer and trying to replace a pdf file that is currently open in adobe reader causes the following exception:

 

System.IO.IOException: The process can not access file "C:\Temp\test.pdf" because it used by another process.
   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost)
   at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access)
   at Microsoft.Win32.SaveFileDialog.OpenFile()
   at Telerik.Windows.Documents.Commands.SaveAsPdfDocumentCommand.Execute(Object parameter)
   at MS.Internal.Commands.CommandHelpers.CriticalExecuteCommandSource(ICommandSource commandSource, Boolean userInitiated)
   at System.Windows.Controls.Primitives.ButtonBase.OnClick()
   at System.Windows.Controls.Button.OnClick()
   at Telerik.Windows.Controls.RadButton.OnClick()
   at System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e)
   [...]

WPF allows running multiple UI threads in a single process. When RadPdfViewer is used in such scenarios, sometimes InvalidOperationException: 'The calling thread cannot access this object because a different thread owns it.' is thrown. 

Scenarios:
- Show Find dialog (or any other of the dialogs available for register in ExtensibilityManager class) for the first instance, the for the second instance.

By specification, when some of the destination parameters have null value, the current value of that parameter is to be retained unchanged (This rule applies for most of the properties). For example, if Location (XYZ) destination is imported and any of the left, top, or zoom parameters is null, the current value of the visual viewport for the specified property should be retained. 

Workaround: Edit the document destinations and set default values. For example if the document contains Location destinations the Left, Top and Zoom properties can be set:
foreach (var annotation in document.Annotations)
{
    Link link = annotation as Link;
    if (annotation != null)
    {
        if (link.Destination is Location location)
        {
            location.Left = location.Left != null ? location.Left : 0;
            location.Top = location.Top != null ? location.Top : 0;
            location.Zoom = location.Zoom != null ? location.Zoom : 1;
        }
    }
}

Some files when opened with PdfViewer will throw a KeyNotFoundException which will be handled. Parts of the text in the file might or might not be missing.

When the file has an annotation with a destination and this destination is missing from the destinations (Dests) collection of the catalogue, KeyNotFoundException is thrown when you try to scroll to the page where the annotation is located. A better behavior would be for nothing to happen when trying to click on the annotation leading to the destination.

When a ToUnicode CMap is defined for Simple Font (TrueType or Type1 font) which maps font character codes to two or more Unicode character values, the extracted text should contain the whole set of characters defined in the mappings. The current implementation of RadPdfViewer takes the first character specified in the ToUnicode mapping which leads to missing characters.