A 3-D printer then builds a polymer model based on this blueprint, much as a regular computer printer reproduces digital documents on paper.
In this sentence, what does "much as" mean?
The key word is "as," drawing a comparison between the two things. "Much" is an intensifier, indicating that the similarity is close but not exact. "Just as" is a similar phrase, indicating an exact likeness.
These phrases serve an additional purpose, disambiguating the grammar of the sentence, as the word "as" has multiple uses and can be ambiguous or at least temporarily misleading. In the example sentence without "much," we might expect "as" to mean "because" (the same way I just used it), but "much as" carries no such ambiguity.
The answer by the-baby-is-you is correct. And I gave a thumbs-up to that answer. However, there is an additional aspect.
... much as a regular computer printer reproduces digital documents on paper.
In this case, "much" does indeed act as an intensifier, and to disambiguate, just as the-baby-is-you indicates.
The other aspect is possibly why this phrase is giving Englishlearner trouble. It also acts to create ambiguity. It's a "weasel word" that deliberately inserts vagueness in the phrase, while also inserting the aura of being specific.
"Much as" a computer printer operates? How much? In what way? What items and actions in each case are comparable? What are the differences?
That is, the writer is trying to draw an analogy (this is like that) but trying to avoid being pinned down on any specifics. He wants to create motivation and acceptance, by holding up this thing that most people are familiar with, rather than create an exact and detailed model of how the two things are similar.
Another way to think of it is: It creates a channel for thinking about 3-D printers (the disambiguation part) but it keeps that channel fairly broad and non-specific (the ambiguous part).
This is a lovely example of how flexible and slippery English can be.