public void Add( 
   ImGearPDETextFlags options,
   int index,
   string text,
   ImGearPDEFont font,
   ImGearPDEGraphicState graphicsState,
   ImGearPDETextState textState,
   ImGearPDFFixedMatrix textMatrix
)

string sampleText = "Russian: Русский Текст. Greek: Κείμενο στην ελληνική γλώσσα. Japanese: 日本  Chinese: 借用本院學術活動中";
    
static void AddUnicodeTextToDocument(ImGearPDFDocument igPdfDocument, string textToAdd)
{
    // Initialize current page attributes.
    const int pageWidth = (int)(8.5 * 300);
    const int pageHeight = 11 * 300;
    ImGearPDFFixedRect usLetterRectangle = new ImGearPDFFixedRect(0, 0, ImGearPDF.IntToFixed(pageWidth), ImGearPDF.IntToFixed(pageHeight));

    // Create new PDF page in document.
    ImGearPDFPage igPdfPage = igPdfDocument.CreateNewPage(-1, usLetterRectangle);

    // This is current text position on the page.
    int xPosition = 20, yPosition = 40;

    // Type of encoding that will be used.
    const string encodingName = "Identity-H";
    ImGearPDFSysEncoding encoding = new ImGearPDFSysEncoding(new ImGearPDFAtom(encodingName));

    // Enumerate all system fonts to find one that can represent our text. Add to the page.
    ImGearPDFSysFont.Enumerate(new ImGearPDFSysFont.ImGearPDFSysFontEnumerate(
        delegate (ImGearPDFSysFont systemFont, object userData)
        {
            // Check the possibility to create font by system font with given encoding.
            ImGearPDEFontCreateFlags flags = systemFont.GetCreateFlags(encoding);
            if (flags == ImGearPDEFontCreateFlags.CREATE_NOT_ALLOWED)
            {
                return true;
            }

            // Check the possibility to create font for unicode text, embedding, and embedding only a subset.
            if ((flags & ImGearPDEFontCreateFlags.CREATE_TO_UNICODE) == 0 ||
                (flags & ImGearPDEFontCreateFlags.CREATE_EMBEDDED) == 0 ||
                (flags & ImGearPDEFontCreateFlags.CREATE_SUBSET) == 0)
            {
                return true;
            }

            // Create the font by system font.
            using (ImGearPDEFont font = new ImGearPDEFont(systemFont, encoding, new ImGearPDFAtom(systemFont.Name.String), flags))
            { 
                // Check this font is able to represent given string.
                if (font.IsTextRepresentable(textToAdd))
                {
                    // Get content that be able to fix the changes.
                    ImGearPDEContent pdfContent = igPdfPage.GetContent();

                    // Integrate text to the current page.
                    ImGearPDEText textElement = CreateTextElement(textToAdd, font, 30, xPosition, pageHeight - yPosition, pageWidth - 40);
                    if (textElement != null)
                    {
                        pdfContent.AddElement((int)ImGearPDEInsertElement.AFTER_LAST, textElement);
                        textElement.Dispose();
                    }

                    // Fix the changes on the page and release content.
                    igPdfPage.SetContent();
                    igPdfPage.ReleaseContent();

                    // Integrate font to the document.
                    if (textElement != null)
                    {
                        font.CreateToUnicodeNow(igPdfDocument);
                        font.EmbedNow(igPdfDocument);
                        font.SubsetNow(igPdfDocument);
                        return false;
                    }
                }
            }
            return true;
        }), null);

    // Release current PDF page.
    igPdfPage.Dispose();
}

static ImGearPDEText CreateTextElement(string Text, ImGearPDEFont Font, Int32 FontSize, int x, int y, int w)
{
    ImGearPDEText textElement = null;

    ImGearPDEColorSpace colorSpace =
        new ImGearPDEColorSpace(new ImGearPDFAtom("DeviceGray"));

    ImGearPDEGraphicState gState = new ImGearPDEGraphicState();
    gState.StrokeColorSpec.Space = colorSpace;
    gState.FillColorSpec.Space = colorSpace;
    gState.MiterLimit = (int)ImGearPDFFixedValues.TEN;
    gState.Flatness = (int)ImGearPDFFixedValues.ONE;
    gState.LineWidth = (int)ImGearPDFFixedValues.ONE;

    ImGearPDFFixedMatrix textMatrix = new ImGearPDFFixedMatrix();
    textMatrix.A = ImGearPDF.IntToFixed(FontSize);
    textMatrix.D = ImGearPDF.IntToFixed(FontSize);
    textMatrix.H = ImGearPDF.IntToFixed(x);
    textMatrix.V = ImGearPDF.IntToFixed(y);

    textElement = new ImGearPDEText();
    textElement.Add(ImGearPDETextFlags.RUN, 0, Text, Font, gState, null, textMatrix);

    colorSpace.Dispose();
    gState.Dispose();

    return textElement;
}