The two biggest things to look at when you want to reduce the size of PDF files are removing objects and downsampling/shrinking the images it contains.
1. Re-create the PDF to reduce PDF file size
A handy trick for reducing PDF file size is to re-create or ‘re-fry’ your PDF. By creating the PDF again you can strip out plenty of unwanted objects, remove tags, and compress images further. You can do this with any tool that supports ‘print to PDF’ functionality. For this trick I’ll use the free free PrimoPDF print driver.
- Open the PDF file
- Open the Print dialog
- Select PrimoPDF from the list of printers
- On the PrimoPDF dialog, click eBooks. (Or to manually control the level of downsampling, choose Custom.)
- Click OK.
2. Reduce PDF file size with ‘Save As’
If you use a PDF editor such as Nitro PDF Professional or Adobe Acrobat you can make use of the ‘Save As’ functionality to trim some fat off your PDF files. Chris Dahl explained it succinctly in a recent post:
PDF files have something that is called incremental updates, where any changes that you make to a document is appended to the end of the file without doing a complete rewrite. This is why the Save feature is much faster than a Save As, and also why PDF files saved this way can be large. The Save As feature will rewrite the entire file and provide you with a smaller file size.
So, to shrink the PDF, do the following:
- Open the PDF in your PDF editor
- In Nitro PDF Professional, go to Nitro PDF Button > Save As. In Acrobat, go to File > Save As.
3. Remove unwanted objects
PDF files can contain a bunch of different objects, including bookmarks, links, annotations, form fields, JavaScript, Named Destinations and embedded fonts — all of which can be removed from an existing PDF file. Like tip two it requires a PDF editing tool such as Nitro PDF Professional or Adobe Acrobat.
- Open the PDF in your PDF editor
- In Nitro PDF Professional, go to Nitro PDF Button > Prepare > Optimize Document. In Acrobat 8, go to Advanced > PDF Optimizer.
- Choose the objects to remove
- Click OK
4. Shrink all images in PDF files
For PDF files that contain many images, downsampling all of them can make a noticeable difference.
- Open the PDF in your PDF editor
- In Nitro PDF Professional, go to Nitro PDF Button > Prepare > Optimize Document. In Acrobat 8, go to Advanced > PDF Optimizer.
- In Nitro PDF Professional, use the slider to select the level of downsampling. In Acrobat 8, in the Images tab, specify the level of downsampling.
5. Shrink individual images in PDF files
If you want more granular control when downsampling you can shrink images one at a time and then view the result immediately. This trick requires Nitro PDF Professional (Adobe Acrobat doesn’t include the functionality).
- Open the PDF file
- Select the Edit Text & Images tool (Ctrl+E)
- Double-click on an image
- In the Format ribbon tab, click Resolution, and then choose the level of downsampling to apply.
