A password is asked although Adobe opens the document without one when the document is encrypted with "Encryption of data using the RC4 or AES algorithms with a file encryption key length of 40 bits." - Version 1 (V 1) Revision 2 (R 2).
Similar cases (V1 R3 and V2 R3) are handled in the following item: PdfViewer: A password is asked although Adobe opens the document without one.
Selecting a column with two or more merged cells, selects not only the selected column but the rest of columns that the merged cells are from. The behavior when working with rows is analogical.
As a result, the glyphs are not measured and positioned properly. The issue applies to the TrueType and Type1 fonts.
The TableCellProperty.Padding property of the "TableNormal" StyleDefinition doesn't take effect in the UI. The same is valid for the TableProperties.CellPadding property.
To work this around, you can manually set the Padding property of all TableCell elements in the RadDocument.
var cells = radDocument.EnumerateChildrenOfType<Telerik.Windows.Documents.Model.TableCell>();
foreach (var cell in cells)
{
cell.Padding = new Padding(10);
}