From the PDF Specification: "An ink annotation represents a freehand “scribble” composed of one or more disjoint paths. When opened, it displays a pop-up window containing the text of the associated note."

Sometimes the Ink annotations are imported as UnsupportedAnnotation and not displayed as expected. In such cases, the annotations could be removed from the RadFixedPage content in the following manner:

foreach (RadFixedPage page in document.Pages)
{
	List<Annotation> inkAnnotations = page.Annotations.Where(a => a.Type == AnnotationType.Ink).ToList();
	foreach (Annotation inkAnnotation in inkAnnotations)
	{
		page.Annotations.Remove(inkAnnotation);
	}
}

Observed when loading a document: 

A rectangle is rendered as a solid rectangle instead of a rectangle with no fill.

It is actually checked and only the appearance is wrong. When the file is saved the checkboxes states are as expected.

This behavior is observed with PdfImportSettings.ReadOnDemand setting only.