Thank you for reaching out to the API Support team here at Constant Contact.
While you can set your PDF to open that way initially with Adobe Acrobat, it may not be a setting that translates when a PDF is opened within a browser, such as when it is linked in an email campaign. Constant Contact won't make any changes to the contents of any files that you import, so the PDF may open in the view you are expecting if the file is first saved to your computer and then opened.
As a side note, if you do need assistance with the Constant Contact product suite in the future, you can post on our general support forum (https://community.constantcontact.com/t5/Need-help-with-something-else/bd-p/advanced_support), email our support team at firstname.lastname@example.org, or reach out to our support team by phone at 866-289-2101.
API Support Specialist