Q:

How much disk space do heroku plans have?

I creating an app that works like an DMS(Document Management System) so my client will be uploading PDF's, XLS's and DOC's.

A:

You don't want to be uploading anything to Heroku, it has an ephemeral file system which is reset on restarts/deploys. Anything uploaded should be uploaded to a permanent file store like Amazon S3
https://devcenter.heroku.com/articles/dynos#ephemeral-filesystem

A:

From How much disk space on the Dyno can I use? of the heroku help site:

Issue
You need to store temporary files on the Dyno
Resolution
Application processes have full access to the available, unused space on the mounted /app disc, allowing your application to write gigabytes of temporary data files. To find approximately how much space is available for your current Dyno type, run the CLI command heroku run "df -h" --size=standard-1x -a APP_NAME, and check the value for the volume mounted at /app.
Different Dyno types might have different size discs, so it's important that you check with the correct Dyno size
Please note:
Due to the Dynos ephemeral filesystem, any files written to the disc will be permanently destroyed when the Dyno is restarted or cycled. To ensure your files persist between restarts, we recommend using a third party file storage service.

The important part here is that it is not the same value for every plans and is possibly subject to changes with time:

Different Dyno types might have different size discs, so it's important that you check with the correct Dyno size

A:

https://policy.heroku.com/aup#quota
Network Bandwidth: 2TB/month - Soft
Shared DB processing: Max 200msec per second CPU time - Soft
Dyno RAM usage: Determined by Dyno type - Hard
Slug Size: 500MB - Hard
Request Length: 30 seconds - Hard

Maybe you should think about storing data on amazon s3?

