解析pdf iTextSharp后，俄语字符显示不正确

Question

我正在尝试使用iTextSharp从pdf文件中的表中获取数据。该表包含切割（解析）后未正确显示的俄语符号。 我这样做：

Dim rect_for_page_one As New 
iTextSharp.text.Rectangle(MillimetersToPoints(39), MillimetersToPoints(33), MillimetersToPoints(163), MillimetersToPoints(297 - 70))

Dim filter As New RegionTextRenderFilter(rect_for_page_one)

Dim strategyOne As ITextExtractionStrategy 
strategyOne = New FilteredTextRenderListener(New LocationTextExtractionStrategy(), filter)

Dim output As New String(PdfTextExtractor.GetTextFromPage(PDFReader, 1, strategyOne))

Code screen shot

如何正确显示俄罗斯符号需要做什么？