Why is My InDesign PDF so large?

InDesign is a fantastic publishing program but sometimes the files on export are too big. Let’s look at why this is and how we can reduce the size.

InDesign PDF is large because of one or more of the following:
Large Document Size
Large amount of Hi Res Images
Pasteboard Objects
Colors not in Use

Let’s look at why each point makes a difference and how we can alter them to reduce the file size without compromising on the quality of the output.

Large Document Size

It goes without saying that large document sizes produce large file output. But InDesign is designed to allow for large page numbers. In fact you can have as many as 9999. But no one is going to risk that! If like me you design magazines you could have 60 -100 pages in a file that all have images or block colors, plus large amounts of text on most pages. On export this produces a large PDF.

There are a few options available to reduce the size of the PDF file but it does depend on the final output of the file: Print or Digital.

If you can’t reduce your page number you could consider splitting your file into sections – 16 pages at a time. If you are sending it to print I recommend you speak with your print shop before you do this. They may advise against this and suggest instead that you share the file through a cloud or simply put it on an external drive and bring it to them.

If your file is for a Digital / Web based job there are a number of options if the document is large.

Exporting as Print but with Smallest File Size selected will result in a much smaller file size.

Also in Options Click Optimize for Fast Web View.
You can also have the Interactive elements unchecked.

If exporting as an Interactive PDF you can reduce the jpg quality to Medium (I wouldn’t recommend any lower) and also the resolution to 96ppi. (Again I wouldn’t recommend any lower).

Interactive PDF Options

Large Amount of Hi Res Images

The more placed items you have in your document the larger your PDF file size will be. If you file is for print there is an optimum that images must be (300ppi) however if you look at your Effective ppi in your Info Panel you may be able to reduce the image size in Photoshop.

Effective ppi

You can also adjust this in the Export Panel, in the Compression tab ‘For Images Above’ if you alter this to 310ppi. This allows your images to remain clear and sharp but reducing your file size.

Compression Trick

If your file is for Web you can reduce your Image resolution even further, but bear in mind that most screens (and phones) now have a resolution of 250 – 300ppi.

If you have any vector images this can also greatly increase your file size. It might be worth editing the file in Illustrator to Save As a PDF and reimport it to InDesign. Especially if it is a logo or graphic that appears multiple times within your document.

Pasteboard Objects

I know that this is something I do all the time. Not good output practice but good continuity work practice. I design a lot of magazines each month and each month adverts from regular contributors are swapped out or rotated. To make my working life easier I leave the alternate ads on the pasteboard, so I don’t have to go searching for them the following month.

Although they are not part of the output file, InDesign still has to scroll through them when the PDF is being created. When the file is ready for output, delete everything that is on your Pasteboard, especially Images.

Pasteboard Items

Colors Not In Use

This is another item I sometimes have to bring back into check. I use a lot of colors in the different documents I produce. And more often than not I’m working from a previous months magazine as a template. There could be a whole range of colors that are not in use.

InDesign has a great function within the Swatches Panel. Right clicking on the top right and Scroll down to ‘Select All Unused’
This will highlight for you all the colors that are not in use within your document. There may be only a couple but I always seem to find there are a lot. Click on the Bin at the bottom and they will be deleted.

Colors Not in Use
Bin All Unused Colors

My last advice is that instead of Saving your file you click the Save As and rename it. This will generate a whole new without any cached items. When you then export it after you have done all the tweaks the PDF will be much smaller.

Here are some other posts you might find useful:

Can I edit PDF from mail?

Photoshop PDF vs PDF

How can I tell if a PDF is CMYK?

Tara Cunningham

My name is Tara. I am a Graphic Designer for the last 25+ years. Designing everything from Wedding stationery to Magazines. I have been using Adobe products since I was in college and know all the tips and tricks that make life a little easier when completing a project. Hopefully you will find the answer to your question on PurpleHotKeys.com

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