Learn Hardcore Indonesian: Saya mencetak dokumen penting di kantor. - I print important documents at the office.

meN- is the active-verb prefix in Indonesian. It turns the root cetak (“print”) into the verb “to print.” The nasal sound in meN- assimilates to the first consonant of the root:

With c (as in cetak), meN- becomes men-, yielding mencetak.
(As a side note, with t or k you’d see meng-, and with s you’d see meny-, each following similar assimilation rules.)

Why are there no words for “a” or “the” in Saya mencetak dokumen penting di kantor?

Indonesian does not use articles. Nouns stand alone, and definiteness or indefiniteness is inferred from context. If you really need “a,” you can add sebuah or satu, and for “the” you can sometimes follow a noun with itu (“that”).

How do I express past or progressive aspects? For example, “I printed” or “I am printing.”

Indonesian verbs do not change form for tense. Instead, you add aspect words or time markers:

Ongoing action (“I am printing”): add sedang → Saya sedang mencetak dokumen penting di kantor.
Completed action (“I printed”): add sudah → Saya sudah mencetak dokumen penting di kantor.
Future action (“I will print”): add akan → Saya akan mencetak dokumen penting di kantor.