Specific laws, you'll probably need to look up based on where you live. Very broadly, copyright is a (limited term) monopoly on choosing who can make copies, end of story, so if you don't have explicit permission, you're not allowed. Historically, companies and the legal system have turned a blind eye to anything that wasn't mass production, but the fact that scanning, uploading, and downloading a document to a private server for your just you creates dozens of copies (on every device it passes through, since that's how transmission happens), companies are more aggressive, if they find out. However, in the United States, there are some transient carve-outs for backing up software and (if I remember correctly) some other kinds of content. But for the most part, you'll mostly be relying on not sharing what you scan to mean that companies can't spot that you're infringing on their monopoly.