Attachments is a controversial topic when sending cold emails to your contacts. Generally speaking, adding attachments have a high chance of sending your email into the spam box and therefore leading to a lower open rate.
To ensure that attachments don't affect email deliverability, branded domains needs to be set up in order to include attachments in your emails. If you're not on branded domains, you'll be prompted to set this up when trying to add an attachment.
Adding attachments to email steps
If you're already set up on branded domains, you'll see the option to upload a file into the email step when you click on the attachments icon.
When you upload the file, it will upload as a link to open the file in a new tab when contacts click on the link.
Linking attachments as text links
If you'd like to have the attachment display as a text link, you can highlight the text to link to, click on the link icon, and then add in the attachment URL in the link box.
Note: Only PDFs, word document files, and images can be included as attachments. The maximum file size that can be uploaded is 26 megabytes.