https://www.cnblogs.com/theyangfan/p/17074647.html
权威的文档：
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PDF Explained （译作《PDF 解析》） | PDF-Explained《PDF 解析》https://zxyle.github.io/PDF-Explained/
https://zxyle.github.io/PDF-Explained/resources/pdf_reference_1.7.pdfhttps://zxyle.github.io/PDF-Explained/resources/pdf_reference_1.7.pdf
PDF Explained [Book]At last, here's an approachable introduction to the widely used Portable Document Format. PDFs are everywhere, both online and in printed form, but few people take advantage of the useful ... - Selection from PDF Explained [Book]https://www.oreilly.com/library/view/pdf-explained/9781449321581/
https://zxyle.github.io/PDF-Explained/