What do I call a person who reads documentation or guides in a cursory or superficial manner?

What do I call a person who reads documentation, guides or tutorials in a cursory or superficial manner, i.e. without doing so thoroughly?

You are referring to superficial or skimming reading:

Deep reading:

• The active process of thoughtful and deliberate reading carried out to enhance one's comprehension and enjoyment of a text. Contrast with skimming or superficial reading.

Superficial reading:

• suggests a lack of thoroughness or a neglect of details ' he gave the letter only a cursory/ superficial reading'.

• Any book intended for the general reader can be understood if you approach it in the right way. What is the right approach? The answer lies in one important–and paradoxical–rule of reading. You should read a book through superficially before you try to master it.

Skimming reading:

• is one of the tools you can use to read more in less time. Skimming refers to looking only for the general or main ideas, and works best with non-fiction (or factual) material. With skimming, your overall understanding is reduced because you don’t read everything. You read only what is important to your purpose. Skimming takes place while reading and allows you to look for details in addition to the main ideas.

I think you can refer to the subject in question as a superficial reader (Ngram) or with the less common definition 'skimming reader'.

Source: www:thegospelcoalition.org

I would call such a person a skim-reader. Here are some relevant dictionary entries for the verb skim:

2.3 [WITH OBJECT] Read (something) quickly or cursorily so as to note only the important points:

he sat down and skimmed the report

[NO OBJECT]: she skimmed through the newspaper

EXAMPLE SENTENCES

She let her eyes skim the page, not really reading it, until she got to verse thirty-nine.

Lacey reached forward and took it, her eyes briefly skimming over the first few pages.

When writing about an author, it's often helpful to at least skim through his latest book.

2.4 (skim over) Deal with or treat (a subject) briefly or superficially.

EXAMPLE SENTENCES

Why would they treat this sultana in such a fashion whereas their counterparts briefly skimmed over her career?

As a conversationalist, Birkin is a whirlwind, skimming over subjects, lifting them up, reshaping them utterly before throwing them back down.

But the media simply skimmed over that subject.

(Definitions of skim and skim over, plus usage examples, from Oxforddictionaries.com)