private Boolean IsValidPDF(String FilePath)
        {
            //force proper handling of all digits and points. 1.2345,67
            CultureInfo.DefaultThreadCurrentCulture = new CultureInfo("el-GR", false);

            ValidationErrorMsg = String.Empty;

            //check if the file is corrupted or in use or something else is wrong with it
            if (DPL.LoadFromFile(FilePath, "") != 1)
            {
                ValidationErrorMsg = string.Format("Error code {0}, while loading file {1}", DPL.LastErrorCode(), FilePath);
                return false;
            }

            //check if the file doesn't contain any text at all so is a 100% image/photo/scan
            if (DPL.HasFontResources() == 0)
            {
                ValidationErrorMsg = "This file doesn't contain any text!";
                return false;
            }

            //check if the file contains images that are big enough (background) to mean that this is not a proper text pdf and should be handled by ocr scan
            Int32 il = DPL.GetPageImageList(0);
            Int32 lc = DPL.GetImageListCount(il);

            for (Int32 i = 1; i <= lc; ++i)
            {
                Int32 imgWidth = DPL.GetImageListItemIntProperty(il, i, 401);
                Int32 imgHeight = DPL.GetImageListItemIntProperty(il, i, 402);

                if (imgWidth > 1500 || imgHeight > 1500)
                {
                    ValidationErrorMsg = "This file seems like an image!";
                    return false;
                }
            }

            return true;
        }