No, attachments are not supported in campaign sequences.
This is a deliberate choice, as attachments can significantly hurt your email deliverability. To help protect your sender reputation and inbox placement, attachments are disabled for automated sequences.
You can still send attachments in the following cases:
Manual replies sent from the master inbox
Programmatic replies sent via the API
If you need to share files as part of a sequence, we recommend using a link to a hosted file (such as a Google Drive or Dropbox link) instead.