Apache PDFBox 1.8.1 发布

Apache PDFBox 1.8.1 发布了，主要是 bug 修复：

[PDFBOX-1515] - PDGraphicsState class receives null page argument leading to NPE
[PDFBOX-1538] - Content of annotation not visible in image (converted from pdf)
[PDFBOX-1547] - TextPosition.getX() and getY() do not work properly with CropBox
[PDFBOX-1549] - TTFSubFont generates bug-prone TTF sub fonts screwing some printers
[PDFBOX-1551] - Merging PDFs with interactive forms results in a corrupt PDF
[PDFBOX-1556] - Saving a document containing a xfa form creates invalid pdf
[PDFBOX-1557] - NonSequentialPDFParser incorrectly parsing document info
[PDFBOX-1558] - Unused PDSignature class should be removed
[PDFBOX-1559] - Error when using monospaced Fonts

PDFBox是Java实现的PDF文档协作类库，提供PDF文档的创建、处理以及文档内容提取功能，也包含了一些命令行实用工具。