The Signeasy app supports document sizes up to 40MB. 

Just a couple of things to keep in mind when in regards to document size:

• Most email providers limit attachment size to 25mb, so if your document is larger than that you won't be able to email it.
• Larger document sizes may take longer to synchronize across your devices or save as drafts.
• Be careful adding images, as they can quickly add to your document size.