.pdf file saved as .do

No, not .doc ... it's .do.

Where you tell me, I don't have any file types where I can create new types... I'm on Windows 7.

Just open an Adobe window, go to file-open, and select the .Do file in question. I think that should work.

Anyone to give me an idea to help me solve my problem?

Method 1:
The best way to save it as a PDF file directly from the text.
1. Open the PDF file, choose File > Save As Text.
2. In the Save As text dialog box, enter the name and location, and click Save. Your file is saved with the extension .txt.
It often generates inaccurate text and simply cannot handle multiple languages (notably Chinese, Japanese, and Korean), unless you use Acrobat Professional.

Method 2:
Use a professional PDF to DOC converter.
It will keep all the formatting, text, and images in the original PDF files, and you do not need to install MS Office or Adobe Reader.
Ad removed Moderation CCM
Method 3:
There are many other online sites. Such as [Ad removed Moderation CCM
But the output files do not have the quality.

.doc can be, right? You're on Windows, aren't you? Which one,
Then try going to Folder Options/Show extensions and, afterwards, change it on the problematic file

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