Learn Spanish (Latin America): El autor sugirió leer un documento antiguo. - The author suggested reading an old document.

In English, we often use the "-ing" form of a verb as a noun (like "reading" in "suggested reading"). In Spanish, when a verb acts as a noun or receives the action of another verb, you almost always use the infinitive form (leer). Using the Spanish "-ing" equivalent (leyendo) here would mean the author was currently in the middle of reading!

Sugirió comes from the verb sugerir (to suggest). Why is there an "i" instead of an "e" in the middle?

Sugerir has a stem change in the past tense (the preterite). For the third-person forms (like he, she, or it), the "e" changes to an "i". So instead of "sugerió", the correct spelling is sugirió.

Why does antiguo come after documento?

In Spanish, descriptive adjectives like antiguo (old) usually come after the noun they describe. This is the opposite of English, where we put the adjective first and say "old document".

Why is there an accent mark on the "o" in sugirió?

The accent mark shows where to put the spoken stress. Regular and stem-changing verbs in the past tense (preterite) for he, she, or it usually have the stress on that final letter, so they need an accent mark to break the normal pronunciation rules (just like comió or vivió).