A document or envelope limit is a tactic that many e-signing solutions use to limit the number of times you can use their service over a set period of time.
DocuSign is the most famous example. The company caps the number of times you can send content from their platform at around 100 envelopes per user/year. If you need to send more, you’ll have to talk to the sales team, who can raise your limit for a fee.
There is an important distinction here, as well. Envelopes are usually considered as something that you put documents in rather than the documents themselves, and that works out to a different calculation based on how you send your content.
For example, RightSignature limits the number of documents you can send to 100 documents per month/user.  So you can send 100 separate documents each month.
DocuSign limits you to 100 envelopes per user/year, but if you needed to send five documents to the same person at the same time, you could package them all in a single envelope and send that out.  Those five documents (if sent in this way) would only use one envelope.
Depending on how you send your documents, and how many you need to send, keeping track of envelopes and document limits can be a huge pain. That’s why PandaDoc allows users to send unlimited documents on every plan. No limits, no restrictions. It’s all included with PandaDoc.