Yes, you can send a communication easily via the CRM Contact Management Portal, and include attachments to it.
To do so in the Web Portal, go to CRM > All Contacts > select the Edit Arrow for the intended Contact > select the Email symbol in the Contact card > select Attachments section in the communication drawer.
You will be led to a Resources drawer, where you can either click / tap the grey section to open a file folder on your computer, or drag and drop from a folder. There will also be a list of Resource Documents that saved in your Formitize account, and you can select the checkbox of whichever you may like to add.
You can also send attachments as part of a form submission, via Form Actions, or attach them to an invoice as a default attachment or as single attachments on an invoice.