A paper I looked up on Academia.edu today turned out to be a scan of pages in which many words have been whited-out with typists' correction fluid. This is a typical sentence:
Unfortunately, the Dirac-Baez Determinant is ill-conditioned for assessing the isomorphism structure of Pauling's high-order valence-bond bundles. [WHITE-OUT] Mac Lane's 2-categorification of taxogellation coefficients on the [WHITE-OUT] [WHITE-OUT] hints at such an outcome ([WHITE-OUT] 1972b; also 1973), while Gordon Pask's electro-neural–swarm dimensionality compression (Pask 1961), as well as Stafford Beer's POSIWID analysis of [WHITE-OUT] (Beer 1972), and Ron Atkin's multidimensional [WHITE-OUT] (Atkins 1972), confirm it for non-dense επι–recodings.
(I have altered words so that I don't identify the person who uploaded the paper.)
The paper is a chapter of a recently published book, and I haven't found any open-access copies. Is this a case of what WBT describes in an answer to Citing paywalled articles accessed via illegal web sharing? WBT says that "Sometimes, the differences [between official paywalled copies of papers and unofficial free ones] are honeypots intentionally inserted by publishers designed to get the message out that only official sites can be relied upon for accurate information."
To clarify following a comment: knzhou suggests this is likely to be a scanning or rendering error. I was going to post a screenshot, but don't have enough reputation. It's immediately obvious to anyone who has used these correction fluids — which I have when cartooning — that that's what they are. Give-aways include the colour, thickness diminishing towards the long edges, brush streaks on the surface, and the way the marks follow the words. I'm not worried about this, though it's annoying to lose the information in the publication, but I am curious. I've never seen this before.