Currently, signature flags, represented by the 'SigFlags' optional entry, are not imported and exported, and there is no API for setting them.
As a result, documents signed with RadPdfProcessing (or with RadPdfViewer) appear in Adobe Reader without the blue document message bar at the top (the analogue of the RadPdfViewer's SignaturePanel).

If the API is supported, setting the flag to 1 or 3 would ensure that the message bar would be visualized in Adobe Reader.

Support conversion of XPS documents to PDF using RadPdfProcessing.

Provide a way to export filters.

When a HTML has a wrong encoding set (content="text/html; charset=utf-16") we use the UTF-16 encoding when importing this HTML. This leads to wrong import. 
Microsoft Word detects that the set encoding is wrong and uses UTF-8 instead so that the imported result is correct. 

The HTML5 specification forbids the use of the meta element to declare UTF-16, because the values must be ASCII-compatible: https://www.w3.org/International/questions/qa-html-encoding-declarations#utf16 

Provide the ability to work with images in headers/footers of a worksheet. Note that large images put in headers are visualized as watermarks on printing/exporting to PDF.

Some customers need to export a single page of the PDF document to plain text. Expose such a possibility so the customers don't need to export the whole document.

The row declaration is the following:

<row r="8" spans="1:18" ht="15.75" x14ac:dyDescent="0.25">

The dyDescent attribute is described as follows:

The dyDescent attribute is a double attribute, as specified in [XMLSCHEMA2/2] section 3.2.5, that specifies the vertical distance in pixels from the bottom of the cells in the current row to the typographical baseline of the cell content if, hypothetically, the zoom level for the sheet containing this row is 100 percent and the cell has bottom-alignment formatting. See section 2.2.4.12 for how this element integrates with the Office Open XML file formats specified in [ISO/IEC29500-1:2016]. The dyDescent attribute has a side effect; it sets the customHeight attribute to true even if the customHeight attribute is explicitly set to false. 

Note: Since the dyDescent attribute is not implemented, the height is not recognized to be custom and therefore it is not imported at all. The row has the default height.

The hierarchical document structure is a means to describe the PDF document structure, which is currently not supported. See 10.6.1 Structure Hierarchy on 856 page of the PDF specification for details.
This document structure is an alternative to the standard PDF structure and most non-Adobe software does not support it.

The document might have been created with Adobe software like Adobe LiveCycle Designer. Very often the document contains some fallback text in the standard PDF structure like:
"Please wait... If this message is not eventually replaced by the proper contents of the document, your PDF viewer may not be able to display this type of document."
"The document you are trying to load requires Adobe Reader 8 or higher. You may not have the Adobe Reader installed or your viewing environment may not be properly configured to use Adobe Reader. For information on how to install Adobe Reader and configure your viewing environment please see  http://www.adobe.com/go/pdf_forms_configure."
"For the best experience, open this PDF portfolio in Acrobat X, Reader X, or later."

Currently the PageOrientation property is used to determine the actual size of the paper to use on the printer and does not reflect document's visualization. In order to affect Section's appearance the user should change the PageSize and PageMargin properties. For convenience the Rotate method is introduced in order to update the properties simultaneously. However the usage of the Section.Rotate(PageOrientation) method is confusing since the properties are not updated when Section.PageOrientation is already set to the same value as the parameter. Also, Rotate method is useful only for rotating already created sections, and to create section with specified pages size and margins the user should set all Section's PageSize, PageMargin, PageOrientation properties anyway.

More convenient API must be provided to create Section instances with correctly set properties for the desired page orientation.

The signature field preserves information about the time of signing through the TimeOfSigning property of Signature.Properties. However, the DateTime object doesn't keep info about the time zone the document has been signed in. Some customers need to obtain this information.

While signing a document in Adobe Reader, the users can lock the document fields from editing. Expose a similar functionality.

The feature is described by the FieldMDP transform method, described on page 736 from the Pdf Reference 1.7

One of the options grouped under alignment is Shrink to Fit. Shrink to fit will automatically reduce the font size until text fits in a cell.