They use very large printers to print the posters commercially. But what about those of us who have small printers at home? Most of people have document printers that can print on A4 or Letter size paper sheets. Now you can use the Poster It software to print a large poster size image on small sheets in parts. Using this software, small portions of the image is printed on many sheets and then you can put together all the sheets to get the large poster.
You can download the Poster It software from the Greatis software website. The download is available in form of an installer. After the installation, you can run it from its desktop shortcut, if it does not run automatically by itself. In the Poster It window, you can click on the Load image button to select an image to load.
The loaded image is shown with red colored split lines which indicates the portions of the image that would be printed on different sheets. The first thing you should do is check the printer settings by clicking on More printer settings and change the paper size and orientation to the correct size. Changing the paper size would re-adjust the split lines.
You can choose to print the large image on multiple sheets, print whole image on one sheet or stretch a smaller image to fit on the paper sheet. You can enlarge or reduce the picture size manually by selecting the picture scale. If you do not have a printer connected, then you can save the different split parts into separate images by clicking on the Save parts. If you want to see a preview of how the image parts would be printed on different sheets, then you can click on the Preview button. In the preview window, you can selectively print individual paper sheets if you want. You can click on the Print button to print all the paper sheets in one go.
So even if you have a printer that can print only on letter size or A4 size sheets, you can still print a large poster using the Poster It software. The large image is split into multiple portions and printed on many sheets which you can put together to get the large poster. The Poster It software is free for personal use but for commercial use you need a license.
You can download the Poster It software from http://www.greatis.com/.