For some documents, the clippings and colors of the geometries are modified on an import-export scenario.

IOException when an object in the cross-reference stream has a negative offset.

"System.IO.IOException: An attempt was made to move the file pointer before the beginning of the file."

When inserting ligature languages text into a block, the text doesn't appear on the generated PDF file.

With the following sample code, the issue can be reproduced:

private static string fileName = "Hello.pdf";
        static void Main(string[] args)
        {
            byte[] fontData = File.ReadAllBytes("calibri.ttf");
            FontFamily fontFamily = new FontFamily("Calibri");
            FontsRepository.RegisterFont(fontFamily, FontStyles.Normal, FontWeights.Normal, fontData);

            RadFixedDocument document = new RadFixedDocument();
            RadFixedPage page = new RadFixedPage();

            string text = "مرحبا";
            var reversedText = text.ToCharArray();
            Array.Reverse(reversedText);
            Block block = new Block();
            block.InsertText(new FontFamily("Calibri"), new string(reversedText));

            FixedContentEditor editor = new FixedContentEditor(page);
            editor.DrawBlock(block);
            document.Pages.Add(page);

            PdfFormatProvider provider = new PdfFormatProvider();
            using (Stream output = File.OpenWrite(fileName))
            {
                provider.Export(document, output);
            }

            ProcessStartInfo psi = new ProcessStartInfo();
            psi.FileName = fileName;
            Process.Start(fileName);
        }

Trying to clone the Signature of a SignatureField leads to InvalidOperationException as the FieldName of the cloned signature is already set.
Workaround: Remove the signatures before the merging of the document:
private static void RemoveSignatures(RadFixedDocument document)
{
	List<FormField> signatures = document.AcroForm.FormFields.Where(ff => ff.FieldType == FormFieldType.Signature).ToList();
	if (signatures.Count > 0)
	{
		foreach (FormField signature in signatures)
		{
			document.AcroForm.FormFields.Remove(signature);
		}
	}

	List<SignatureWidget> signatureWidgets = document.Annotations.Where(a => a.Type == AnnotationType.Widget && a.GetType() == typeof(SignatureWidget)).Cast<SignatureWidget>().ToList();
	if (signatureWidgets.Count > 0)
	{
		foreach (var signatureWidget in signatureWidgets)
		{
			foreach (RadFixedPage page in document.Pages)
			{
				if (page.Annotations.Contains(signatureWidget))
				{
					page.Annotations.Remove(signatureWidget);
				}
			}
		}
	}
}

Wrong encoding is used when the PDF file contains font with custom encoding

Workaround:

foreach (var widget in field.Widgets)
{
    widget.TextProperties.Font = FontsRepository.Helvetica;
}