What are the default copyrights/IP restrictions for a work I post online?
In most (possibly all) jurisdictions, the default for a creative artifact with no license information attached is that it assumed to be all rights reserved.  In other words, another person cannot do much of anything with it besides look at it.

See, for example, GitHub's information about "no license" licensing. They are talking about code, but the default they mention is general.

Note that there are certainly categories of work for which this does not apply (for example, recipes are specifically not protected under US copyright law), but it most certainly applies for any substantial paper draft.