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I can see you are trying to do it correctly, but you do face a bit of a minefield.
If you sell a tutorial that carries no copyright notice, you might get away with it as long as the author doesn't complain. However, the site you copied the tutorial from (assuming you did) may have terms and conditions that state that intellectual property rights are retained by the site owners, or their contributing authors.
If you re-purposed a tutorial in a different format, i.e. converted 10 web pages + images into one downloadable PDF file, you would be creating a 'new' work, albeit based on someone else's writing. To be honest, that may be what the original author did! - copy bits of info from here and there and put it all together. If you included a credit to the original author they may not object, but no guarantee.
If you are looking at this as a business, I am sure there are e-book 'wholesalers' who will sell you books at cost with a licence to re-sell. I believe a lot of commercial e-books are protected using DRM to prevent re-distribution. Actually, this is a bit restrictive. You can sell an old Harry Potter book in a car boot sale, but you probably can't put the e-book version on eBay.
Bigger question is... will anyone buy tutorials? The internet is awash with free ones.
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