Some pdf file can be read normally with Chrome and other pdf readers, but in zotero pdf reader, the font changes from serif to sans serif, with abnormal spacing.

E.g.
https://www.researchgate.net/profile/Steven-Quartz/publication/2600497_The_Neural_Basis_of_Cognitive_Development_A_Constructivist_Manifesto/links/55ae5b9e08aed9b7dcdd98c4/The-Neural-Basis-of-Cognitive-Development-A-Constructivist-Manifesto.pdf