Hi @kim s thank you for posting in the community! Just to confirm you would like your colleague to edit the document - is this correct? In that case it may be suitable for your use-case to create a duplicate of your document and share that with your colleague. 

To duplicate a document simply right-click it in your documents list and select 'Duplicate'. 

Alternatively if you only wish for your colleague to view / comment on your document you can share it with can view OR can comment permissions. For more information on the different sharing settings I recommend taking a look at our Share with collaborators in Lucid article from the Help Center. 

I hope this helps. Please feel free to let me know if this is not what you are looking for or if you have any questions!