Let $Pres$ denote the 2-category of locally presentable categories (categories that are accessible/cocomplete), cocontinuous functors, and natural transformations. Let $Cat$ denote the 2-category of (small) categories, functors, and natural transformations. There is an inclusion functor $i:Pres\hookrightarrow Cat$. Does this admit a left/right adjoint?



Adjunction between locally presentable and ordinary categories?
Size conditions are not such a big deal when it comes to formulating the question, at least. We just let Cat be the non-locally-small 2-category of locally-small categories (perhaps we require that the object sets be no bigger than the universe, it turns out not to matter). The inclusion $\mathsf{Pres}^L \to \mathsf{Cat}$ preserves reasonable 2-limits, but not 2-colimits, see [here](https://mathoverflow.net/questions/152251/reference-request-colimits-of-locally-presentable-categories). So it might have a left biadjoint but it certainly does not have a right biadjoint.


But we can show that size issues *do* prevent the left biadjoint from existing. Let $C$ be a discrete category with object set $C\_0$ of the size of the universe. Then if $FC$ were a reflection of $C$ in $\mathsf{Pres}^L$, we would have $\mathsf{Pres}^L(FC,D) = \mathsf{Cat}(C,D) = D^{C\_0}$ for any locally presentable $D$. If $D = \mathsf{Set}$, say (the category of *small* sets), it's easy to see that $D^{C\_0}$ has the cardinality of the powerset of the universe. But the hom-category $\mathsf{Pres}^L(E,D)$ between any two locally presentable categories is no bigger than the size of the universe (this is because any cocontinuous functor $E \to D$ is the left Kan extension of a functor defined on the small subcategory of $\lambda$-presentable objects for some $\lambda$; there are at most universe-many such functors, and taking the union over $\lambda$ still yields universe-many). So no such $FC$ can exist.


Along the lines of Dennis Nardin's comment, though, the inclusion of [locally *class*-presentable categories](https://arxiv.org/abs/1110.0605) into $\mathsf{Cat}$ has a left biadjoint given by sending $C$ to the [free cocompletion](https://ncatlab.org/nlab/show/free+cocompletion) of $C$ (which is the full category of presheaves $PC$ on $C$ when $C$ is small, but a proper subcategory of $PC$ when $C$ is large). 


