Ruby on Rails

Basically, I need to generate reports which contains more than 300 tables, over 100 charts and many images. Until now this was done manually in docx, so I was asked to build an RoR app where the user could add all the images and data, and with one button click get the report. Here is the problem. The user wants to be able to download the report, and be able to edit that file manually.
So I looked for gems. Many of them just fill spaces in docx files. At the moment I use axlsx to generate my charts, tables and images, everything is saved into excel file. It works pretty well. I was thinking if there is some kind of format that ruby can edit (insert tables, bar charts, styles...) and the same format could be opened in the office.... why ? because I could open the file and convert it to docx..
I am a little lost. My web app have database ready, just need some way of generating that file for the user. Any tips would be nice. I thought about html reports, but I cant edit them later, or can I ?
Thanks community.