When choosing the print options in gantterAi™, you can choose to generate PDFs for the "Task List" and the "Gantt Chart" separately. This may help it to fit better on one page when printing.
GantterAi™ generates the PDF as a single-page. The steps to break it up into multiple pages so the print is larger depends on your PDF software and your printer. This link can give you instructions to print as multiple pages using Adobe Reader: https://helpx.adobe.com/acrobat/kb/print-posters-banners-acrobat-reader.html
Another thing you can try is choosing the "HTML" print option from gantterAi™ instead of PDF. You can then print the same as any web-page.
Printing Plan Boards:
As for printing boards and tags there is something called “Smart Wall Print”. This is where you can print a massive version of your project on a plotter to share with your entire team for easy access and viewing.
To access it click on the icon that looks like a file with writing or a list on it (This Icon is not very obviously a print button at all). Under here you will see some different reports you can repair about specific aspects of your project and the smart wall print option.
Click on this and gantterAi™ will then generate a preview of your board and this is where you can also adjust sizes and other specifics about the print then hit print and your board will print to whatever default printer your computer is connected to.