Celoxis offers you various options to print your project schedule.

Visible - The downloaded PDF will have the copy of what you see on screen.
Complete - The downloaded PDF will have the copy of your entire project with the selected width.
Custom - You can select the Start and End date of your project's schedule that you wish you view.

The Fit Width option lets you choose the paper width for the PDF to adjust to that size. After you hit Submit, the PDF of your project plan will be downloaded.

Your hidden columns, i.e., the open ones that are overlapped by the Gantt Schedule will not appear in the PDF.
So will the collapsed parent-child nodes; you will have to manually expand them. Only when you print the Complete schedule, will they be expanded by default.
The Scale and the print option you select will decide the what will be printed. If the image size exceeds 25,000 (height) and 10,000 (Width), you will be prompted to reduce size. In such cases, you can select the Custom option and select date ranges to print the Gantt.

After printing the Gantt, if the PDF/PNG image does not download, then ensure that the pop-up is not blocked. You will see an icon indicating this in the browser's URL on the right-side. After you allow this, the PDF/PNG will be downloaded successfully.

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