User guide

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Image optimization settings
Optimizing images in your PDFs allows you to create the perfect balance between file size and visual
quality, depending on how your files are to be used. There are two primary techniques used in optimizing
images: compression and downsampling.
Compression
l Lossless: Reduces the file size of an image file without loss of data, by removing only repetitive
information. If an image is compressed using a lossless compression technique, it is identical to the
original in visual quality, and can be useful if you need to extract the images for editing later.
l Lossy: Eliminates "unnecessary" bits of information from the image. Because lossy compression dis-
cards data, it can achieve smaller file sizes than lossless compression, but may not be suitable for
high-quality printing, or if you later need to extract the image for editing or reuse.
Downsampling
Downsampling reduces image resolution by lowering the number of dots per inch (DPI) that the image
contains. Since there is less information that needs to be saved, the resultant PDF file sizes can be
considerably smaller. In general, it is a good idea to downsample images based on the resolution of the
device you are sending the file to. For example, typical computer monitors have a resolution between
72dpi and 96dpi, which is the highest resolution the monitor can display.
Available Image Optimization Settings
The following image optimization settings are available when using Nitro Pro 9's Optimize PDF tool:
Web
Creates files optimized that are optimized for on-screen viewing. Images will be compressed using a lossy
compression technique, and images with resolution greater than 150dpi will be downsampled. Use this
setting when you want to create the smallest possible file size and where print quality is less important
than file size, for example in preparing PDFs for display over the web.
Office Quality
Creates files that are optimized for printing to standard home or office printers. Images will be
compressed using a lossy compression technique, and images with resolution greater than 300dpi will be
downsampled. Use this setting when you want to create a file that retains decent print quality when
printed to a general use printer, while remaining relatively compact in terms of file size, for example in
preparing PDFs for emailing to coworkers.
Professional Quality
Creates files that are optimized for printing to professional-quality printers. Images will be compressed
using a lossless compression technique (pixel information will not be discarded), and images with
resolution greater than 600dpi will be downsampled. This setting creates high print-quality files, while
reducing file size as much as possible, and is ideal for files intended for commercial printing.
Nitro Pro 9 - User Guide