从乱码的PDF中提取文本

我有一个包含重要文本信息的PDF文件.

I have a PDF file with valuable textual information.

问题是我无法提取文本，我得到的只是一堆乱码.如果我将文本从PDF阅读器复制并粘贴到文本文件中，也会发生同样的情况.即使在Acrobat Reader中，文件->另存为文本也会失败.

The problem is that I cannot extract the text, all I get is a bunch of garbled symbols. The same happens if I copy and paste the text from the PDF reader to a text file. Even File -> Save as text in Acrobat Reader fails.

我已经使用了所有可以使用的工具，结果是相同的.我相信这与字体嵌入有关，但是我不知道到底是什么?

I have used all tools I could get my hands on and the result is the same. I believe that this has something to do with fonts embedding, but I don't know what exactly?

我的问题:

• 这种奇怪的文本盗版的罪魁祸首是什么?
• 如何从PDF中提取文本内容(通过编程，使用工具，直接操作位等)?
• 如何修复PDF在复制时不显示乱码?

• What is the culprit of this weird text garbling?
• How to extract the text content from the PDF (programmatically, with a tool, manipulating the bits directly, etc.)?
• How to fix the PDF to not garble on copy?