There is no storage limit on your Process Street account, however, there are individual upload limits for various file types.
Workflow upload limits
Videos: 5 GB
(MOV, MPG, AVI, FLV, F4V, MP4, M4V, ASF, WMV, VOB, MOD, 3GP, MKV, DIVX, and XVID videos)
When uploading a video to a workflow, the maximum size is 5 GB. You’ll need to use the upload widget and not drag and drop a video onto the workflow. Embedding a video from Youtube, Vimeo or Wistia has no limit.
Images: 250 MB
When uploading an image to a workflow, the maximum size is 250MB.
(GIF, JPG and PNG images)
Other File Types: 250 MB
(Any other file type, like Documents, Powerpoint, etc.)
Workflow run attachment limits
Attachments must be under 250 MB each.