Hi David thanks for posting in the Lucidchart Community! The size of your document can depend on a few different factors: 

• Number of Shapes


• 
  Revision History: If you have a document that you have been changing incrementally for many months or years there will be many iterations of that document (from the revision history) taking up storage space in your account. Once you find the large document you can reclaim your storage by making a new copy of the document (this new copy will not have the revision history and because of this will take up less storage) and deleting the old version of the document. Note that the old document will take 7 days to permanently delete from your trash and free up storage.
  


• Images generally take up the most space in your account if you are running out of room it is recommended that you clear out as many images as you can from both your documents and your Image Manager. You can access your Image Manager by clicking the image icon next to the magnifying glass above your shape library.

You can check how much of your storage is being used and what it is being used by in the bottom left corner of your Account Settings. If you hover over each of the colored sections you can see what that portion of the storage represents.

The difference between free and paid accounts is that the free account is always limited to 3 documents no matter if their total size is smaller than the account storage limit. In paid accounts you can create an unlimited amount of documents until their total size reaches the storage limit. Since the size of documents depends on the number of shapes images and iterations the maximum number of documents in paid accounts varies from user to user.

If you want to learn more about the differences between the account levels please refer to the Account Types Help Center article.

Hope this helps!

Thank you but this is really false advertising. You cannot have unlimited documents if the number of documents is limited by storage. Any user who creates a reasonable number of documents (somewhere between 20 -100 given the huge storage size a single document consumes) will be in a very bad situation of discovering their unlimited number of documents is suddenly capped and no more documents can be created.

At very least these plans must have more storage space - I can't purchase a plan that is so limited and it is very aggravating to realize it took me three months to figure out that this could be an issue - thankfully I spent some time looking carefully at the account types and differences before paying any money.  The thing that really caught my eye was that the paid plan and free plan both have 1Gb storage - which makes the paid plan just as limited as the free plan).

I would gladly sign up for the paid plan if I knew I wasn't going to run out of storage in a few months.