Update multiple docs using Logstash

Hi

I have two data sources which will be ingested separately using Logstash into elasticsearch, one containing page data from larger documents, the other containing metadata around those same documents

e.g.
source 1: {"name": "Lord of the rings", "page" 1, "content": "Three rings for elven kings under the sky..."}
source 2: {"Author": "JRR Tolkein"}

Creating each document from source 1 is done through logstash, however is there a simple way to then apply the metadata to each page

Desired output:
{"name": "Lord of the rings", "page" 1, "content": "Three rings for elven kings under the sky...", "Author": "JRR Tolkein"}
{"name": "Lord of the rings", "page" 2, "content": "...", "Author": "JRR Tolkein"}
etc

Thanks in advance