RadPdfViewer partially supports CCITTFaxDecode (that is basically TIFF). There are some limitations that are not supported at this stage like EncodedByteAlign = true or Group 3, 2-D encoding.

They are used by the page and the XObjects drawn on it and deal with the overlaying of the colors. These groups are described on page 556 of PdfReference 1.7. 

Bitonal image scaling algorithms which improve the readability of bitonal, black and white images. Due to the lack of colors within the palette of 1-bit black and white images, they become splotchy and distorted when zoomed in or out

Add PrintPreview dialog visualizing the way the document is going to be printed.

Add built-in localization for the UI control and its tooltips. Currently they can be localized by expanding the XAML of RadPdfViewerToolBar and adding the required resources to the code.

In Adobe and Foxit readers, the user can draw different shapes, which are later saved as images in the document.

An implementation of JPXDecoder should be created to allow the decompression of data encoded using the wavelet-based JPEG2000 standard.

Guidelines of how to provide a custom implementation of the JPXDecode filter can be found in the Customize Rendering section of the documentation and a sample implementation can be found in the SDK examples.

Add UI for adding comments and ability to save them. Comments are represented in the document model as text annotations (annotations with Subtype Text). 

Currently, RadPdfViewer uses WPF DrawingContext class for drawing page elements to a Canvas.  When PDF page has many content elements (usually geometries) drawing the page may be time-consuming and freezes the UI. 

Instead, we should consider implementing another approach for rendering the content asynchronously which would improve the user experience. 

When using CTRL+Mousewheel to zoom in to a PDFViewer document, it should zoom into the point where the mouse pointer is located. Currently it just does a simple zoom of the whole document.

For example see Acrobat Reader or Google Maps.

This would allow switching the focus between form field controls by using the Tab key.

As a <role> I want <ability> so that <benefit>.

Represents Highlights PDF content. While the other annotations are drawn on top of the content, the highlight annotation is behind the text it highlights. In other words, it has to be inserted at a specific place in the ContentElementsUILayer. The precise place where the highlight should be placed is described in the PDF file with the BDC, MCID and EMC operators. At the moment, we have implemented a read-only rendering for all annotation types which draws the annotions separately from the page content. In the case of Highlight, the annotation is drawn below the other content. With this implementation, depending on the PDF content, the highlight annotation might be visible or it might not be because in some cases there is geometry content below the highlighted text which hides the highlight annotation appearance. 

A rubber stamp annotation displays text or graphics intended to look as if they were stamped on the page with a rubber stamp. When opened, it displays a pop-up window containing the text of the associated note.

Most PDF viewers have option (enabled by default) which allows fields to be highlighted with colors predefined in the settings. Required fields are highlighted using different color.

For example: In Adobe Acrobat Reader DC this is enabled in "Edit" -> "Preferences" -> "Forms" -> "Highlight Color" -> "Show border hover color for fields". 

Layers represent groups of optional content which can be hidden or shown.

When users do "copy" operation, add the content to the clipboard in RTF format. This would allow to paste the text along with its formatting in text editors like MS Word.

Allow passing specific pages (e.g. "1, 4, 6") and more than one page range (e.g. "1-3, 6-7") to the print dialog`s Pages page range.

Provide public API for accessing document properties such us Title, Author, Subject, Keywords, Creation date, etc...

Add support for interactive forms based on the Adobe XML Forms Architecture (XFA). XFA specifies an XFA resource, which is an XML stream that contains the information of the form. The format of an XFA resource is described in the XML Data Package (XDP) Specification. The XFA resource provides most of the information about the form; in particular, all form-related events such as calculations and validations.