What word means someone who’s satisfied with superficial knowledge?

I used to know this word but cannot remember it.

Basically it’s someone who likes the prospect of being knowledgeable about many things, or at least wants the appearance of erudition, but who is unwilling to put in the time and effort to learn new things.

He may put in just enough effort to learn some trivia to impress others.

And pretentious isn’t the word I was thinking of.

Perhaps dilettante or dilettantish conveys what you describe.

According to Merriam-Webster Online dictionary:

a person whose interest in an art or in an area of knowledge is not very deep or serious.

Plural: dil·et·tantes or dil·et·tan·ti

Per Collins English Dictionary:

sciolist — (rare) a person who gives their opinion on subjects of which they have only superficial knowledge

I can imagine use cases where shallow would work in the meaning you're asking for:

shallow, adj

lacking depth of intellect or knowledge; concerned only with what is obvious

"shallow people"; "his arguments seemed shallow and tedious"

Source: English Wordnet

I would describe this person as a know-it-all. The central definition of that term is slightly different ...

know-it-all n. One who claims to know everything and rejects advice or information from others.

... being more about the refusing to listen to other people on topics where they are actually more expert, but it can certainly be used to describe someone who likes to show off their superficial knowledge of many subjects, and I think it will be more readily understood than some of the other suggestions. In particular, dilettante is more often used to describe someone who has a superficial knowledge of one or two specific subjects, and the other suggested words are quite rare.

You may have been thinking of a smatterer in some topic.

Of smatterer the OED says:

One who has only a slight or superficial knowledge of (now rare) or in a matter; a dabbler. Also used without const.

For which two of the numerous citations given are this pair separated in time by a couple of centuries:

• A. 1680 Butler Rem. (1759) I. 213
  As Smatterers prove more arrogant and pert, The less they truly understand an Art.

• 1893 Jessopp Stud. Recluse Pref. p. ix,
  A clergyman with a cure of souls··must give up all hopes of being anything but a smatterer in science.