The best source for the official printable forms is the Occupational Health & Safety Administration website. The 300A form is a type of injury and illness form to be used during record keeping. These forms are available in .pdf form directly from the OSHA website and are free of charge.
The website actually recommends that users save the file to their computer, using the right click of their mouse and the "save as" option. This will make the file easier to view and help prevent printing issues using a plug in or an app. This also gives the user the option to change the orientation of the page and how it prints since the file is not set up for standard paper measurements.