It is not too difficult to downsample image of PDF document in your Mac OS X system if you can use the application PDF Image Downsample Tool for Mac as your tool. It supports to downsample image with several kinds of types, specify downsample resolution and use different kinds of compression methods for PDF image, which can reduce the size of PDF document in significant measure.
Only three parts are involved in this work after you download and install PDF Image Downsample Tool for Mac in your Mac OS X system, please see the following contents of this page:
1. Open application and add PDF
Please double click the application icon or you can right click the icon and choose Open option in popup floating item to open PDF Image Downsample Tool for Mac. In the opened main window of the application shown in Figure 1, please click Add button to open file picker window for selecting PDF document which need to downsample image into the file list. You can also use the convenient way—dragging and dropping PDF document into the file list. The button Remove can be used to delete PDF file from file list one by one. The button Remove All is for clearing the file list.
Figure 1
2. Downsample image of PDF document
Please click Option button for opening Option dialog box in which you can set parameters for the target file. By clicking Image button on the left, you will see Image Tab on the right, in which you are able to downsample image. Please see it in Figure 2.
Figure 2
In this Tab, you can deal with three kinds of images: color image, gray image and monochrome image. To all of them, you can set downsample type as Bicubic, Average, Closed and Subsmple in Downsample Type spin box to reduce the image pixel and specify downsample resolution in DPI manually in Downsample Resolution edit box to reduce image resolution. To color and gray image, you can use three kinds of compression modes: Auto, ZIP and JPEG. To monochrome image, you can use Auto, ZIP, RLE, JBIG2 or CCITT Group 4 compression method to compress the image. Then please click Apply button to save all the parameters you have made.
3. Start to downsample image of PDF
When you see the main interface of PDF Image Downsample Tool for Mac again, please input the output location in Output Folder text box. You can also click the button besides the text box to open a window in which you can choose an existed output location or create a new one. Then click Start button for starting to downsample image to reduce the file size.