Hi @robert h thank you for posting in the community! That is a great question there isn't any specific maximum file size for Lucidchart.

However please note that if your document is large and has many page tabs large canvases on each tab and a high number of shapes on each canvas it will increase the time it takes to load and update when changes are made. For more information about working with large documents in Lucid I recommend reviewing the 'Large Documents' section of this Help Center article. 

I hope this helps. Please feel free to let us know if you have any questions about this!