These threads may be of help:
https://www.edaboard.com/threads/315662/
https://www.edaboard.com/threads/308812/
https://www.edaboard.com/threads/328062/
Each thread has a list of related discussions toward the bottom of the page. If you visit those threads, they should lead to others which have further information.
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Paint is merely a basic graphics editing program that comes with Windows. You really need higher quality software, if you wish to make diagrams that appear professional.
I think I have seen text become blurry and fringed with colors in Paint, after I create it and then try to manipulate it (example, enlarge it).
There are tricks you might develop, which allow you to perform higher functions in Paint, but they are likely to take up your time.
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Previous thread about software for drawing schematics.
https://www.edaboard.com/threads/307889/