Foxit PDF Editor supports the size optimization of scanned PDFs during PDF creation from a scanner or by choosing File > PDF Optimizer > Optimize Scanned PDF in an existing scanned or image-based PDF. See also The Optimization Options in Custom Scan. 

There are six panels where you select advanced options for PDF optimization: Compress Images, Unembed Fonts, Transparency, Discard Objects, Discard User Data, and Clean Up. 

The Compress Images panel

In the Compress Images panel, you can select options to specify downsampling and compression for color, grayscale, and monochrome images.

With the Advanced Optimization command, you can select professional settings to achieve advanced PDF optimization. To optimize PDF with advanced settings, please do as the following:

You can use the Reduce File Size command to quickly optimize documents with the default settings, which are suitable for a wide range of documents. With this command, you can also reduce file size for multiple files at the same time. To reduce file size with default settings, do as the following:

1. Choose File > PDF Optimizer > Reduce File Size.

2. To apply the settings to the current file, choose Current File. A dialog box pops up. 

• Select multiple images > right-click one of them > Properties…
• A dialog pops up with an Appearance tab. Follow the steps specified in “Setting properties of an image”.

You can adjust multiple images with the same height, width, or both. Select one of the images as the anchor, and the rest of the images will be resized with the same height or width as that of the anchor image.

Below is an example:

This function will be available when selecting three or more images.

This function enables you to center the selected images as a whole vertically, horizontally, or both. To center the selected images, select a type of centering from the Format tab in the right panel, or right-click the anchor image > Center > choose a type of centering.

Below is an example:

• Select two or more images that you want to align.
• Select a type of alignment in the Format tab in the right panel, or right-click the anchor image and choose Align.

To select multiple images, do as the following:

1. Select the Select Annotation command or the Image Annotation command.
2. Press and hold Shift or Ctrl and click the images you want to edit. 

Note: When you right-click or Ctrl-click one of the selected images, it will be highlighted in red, indicating that it’s the anchor image.