Generally speaking, attaching PDF's or other files to emails can flag your recipient's email security (spam filters and firewalls), as well as slow down or stop your email sending, due to the increased size.

To give your email the best chance of reaching your recipients, we recommend that you upload and host your file somewhere*, and then link to it from an image, hyperlink or button in the email editor.

* e.g.: Upload the PDF to your Google Drive, set access permissions for the file to "anyone with the link", and then copy the link.
HINT: You can test that your hosted file is publicly accessible by opening your copied link in an "incognito" browser tab.

The additional benefit of this method is that it allows you to track engagement (link clicks) with the file, to better understand how many of your contacts are interacting with it.

You can also automatically follow-up with contacts who engage with the link, sending them content that you know they're interested in. *

* Learn more about this in The "Clicked Link" campaign trigger" and The "If Clicked Link" campaign condition.

You can also replicate a PDF in your ActivePipe account by using Image & Text panels.