[Compression Options] tab

Select this to compress text and line art.
When you select [Text and Line Art Compression], text and line art (drawings) in the original document will be compressed in Zip format.
Selecting [Text and Line Art Compression] does not result in any degradation in the text and graphics.

Select this to output the PDF file in ASCII 7-bit text format.
The PDF file output in ASCII text format can then be displayed and edited using an application such as text editor.
When [ASCII Format] is not checked, the PDF file is output in binary format. There are usually no problems with the binary format.
Outputting in ASCII format results in a larger file size compared to binary format.

Select this if you want to use downsampling, and select the interpolation from the box at the right.

Calculates the average value of adjacent pixels and replace the entire area with the average pixel color of the specified resolution.
The image quality will be lower than the bicubic method, while the data size will become smaller.

Performs the same processing as the bilinear method in a wider scope.
The gradation of an image will be smoother than the bilinear method, while the data size will become larger.

Reduces jagged edges that are generated on diagonal or curved parts of the outline of an object drawn in an image.

Select this if you want to compress a color image or grayscale image, and select the appropriate compression method in the box at the right.

This is an advanced variant of JPEG described below and achieves improved image quality through lower noise and other enhancements, and superior compression rate compared to JPEG. [JPEG2000 (Quality-Lowest)] applies maximum compression and [JPEG2000 (Quality-Highest)] applies minimum compression.
The size of the file can be reduced by compression, but the higher the compression rate is, the lower the image quality becomes.

This is suitable for an image with a high resolution and large file size, or for continuous-tone images such as photographs.
[JPEG (Quality-Lowest)] applies maximum compression and [JPEG (Quality-Highest)] applies minimum compression.
The size of the file can be reduced by compression, but the higher the compression rate is, the lower the image quality becomes.

This is suitable for monochrome images that consist of large solid areas of black and white.

This is suitable for comparatively small images with many components of uniform density and without gradation such as illustrations and screen shots.
There is no image quality degradation in Zip compression, but the compression rate is low and the file size will be large.

Can be set by selecting JPEG2000 or JPEG in [Compression Method].
If Zip format is more efficient in reducing file size than the selected compression method, Zip format is automatically applied.
The processing speed will be slow due to additional processing for auto select.

Select this to compress black and white images, and select the appropriate compression method in the box at the right.

These are the methods that are used for fax transmission and suitable for monochrome documents created using a graphics application.
These methods are free from loss of data due to compression, and support most image compression formats.
[CCITT Group 4] has a compression rate three times greater than that of [CCITT 3].

This is suitable for monochrome images that consist of large solid areas of black and white.

This is suitable for comparatively small images with many components of uniform density and without gradation such as illustrations and screen shots.
There is no image quality degradation in Zip compression, but the compression rate is low and the file size will be large.

This is the best compression method for reducing the file size of black and white images, but the processing speed will be slow.