Spire.PDF 9.3.4 ではフォントを PDF に埋め込む機能がサポートされました

PdEmbeddedFontConverter converter = new PdEmbeddedFontConverter ("InputFile");
convert.ToEmbeddedFontPdf("resultFile");

PdfDocument pdf = new PdfDocument(inputFile);
pdf.LoadFromFile(inputFile);
for (int c = 0; c < pdf.Pages.Count; c++)
{
    PdfFormWidget formWidget = pdf.Form as PdfFormWidget;
    for (int i = 0; i < formWidget.FieldsWidget.List.Count; i++)
    {
        PdfField field = formWidget.FieldsWidget.List[i] as PdfField;
        if (field is PdfButtonWidgetFieldWidget)
        {
            PdfButtonWidgetFieldWidget buttonWidget = field as PdfButtonWidgetFieldWidget;
            PdfHideAction hideAction = new PdfHideAction(buttonWidget.Name, true);
            buttonWidget.MouseDown = hideAction;
        }
    }
}
pdf.SaveToFile(outputFile);
pdf.Dispose();

PdfCompressor compressor = new PdfCompressor("1.pdf");
compressor.Options.TextCompressionOptions.UnembedFonts = true;
compressor.Options.ImageCompressionOptions.CompressImage = true;
compressor.Options.ImageCompressionOptions.ResizeImages = true;
compressor.Options.ImageCompressionOptions.ImageQuality = ImageQuality.Low;
compressor.CompressToFile("1_out.pdf");