How do I make my PDFs smaller?

Small bug on a big flowerWhat happens when the PDF you want to send is just too big?
How can you make that PDF (or an image, for that matter) smaller?

I got a great question about file sizes from a reader today.

The file size of the current issue of my church’s newsletter is too big to upload via WordPress. So can I use ftp to put it in a new folder and just link to it?

Or is there an easy way to reduce the size of a PDF?
Do you have to make the images smaller you put in it? or the number of photos? or run it through some compression? or?

Not only does uploading a big file to the internet make WordPress choke, but remember: the time it takes to upload is directly proportional to the download time.  Smaller images will definitely help!

Uploading does generally takes longer. But if the file is too big for WP, it’s just plain too big.

Let me ask you, just how long will you wait for a file to download before you decide you don’t really care that much anyway?

If your reader doesn’t even download the file, none of your content has any value anyway.

So here’s my answer, with first a bit of background

Think about images you make on your digital camera (or even phone!).  If you don’t know anything about these things at all, it’s all about the number of dots that can be squeezed into the space. And for sure you’ve been taught to know that 10 megapixel camera is MUCH better than a  2 megapixel camera.

Also, what happens when you try to attach an image you took with your phone to an email? My phone asks me to choose the image size: small, medium, large, and full size.

And if you load one of those giant photos onto your computer, have you noticed how long it can take to show the whole thing? It’s sure more than instantaneous.  That’s because the file is HUGE!

So what can you do? Edit the image size!

You could just use the image editor that’s part of WordPress (or MSWord, for that matter) to drag the corners and make the image the right size. The problem is you haven’t actually changed the size of the photo. The original giant photo in still in that file, just shown at the size you want. That’s easy and works great if you don’t care how big the final file is.

But reducing the size of the PDF is what we’re headed for.

Here are some suggestions to make your PDF file smaller

1. Use fewer images

Do you really need 6 views of your wedding cake in your Holiday letter? I’m guessing, in reality, nope! Just pick the best one. (Your friends REALLY don’t care to see all 6!)

2. Reduce the size of the photos you do use

  • Start by making the photo the actual size you want to use.

You don’t need a fancy graphics program to do this.

I like to experiment with the actual sizes so I use Irfanview. It’s free, loads up fast and is powerful enough to massage the size of the photos. It actually does lots of stuff and it’s pretty intuitive. Preview will probably work for a Mac.

Make the image bigger and smaller. But remember (or FYI) you lose a little quality in the image with each resizing. So for the best quality, when you’ve decided on the final size, go back to the original giant image and make the reduction all at once.

  • Pay attention to the resolution of the image.

Here’s a file size comparison

Bigger numbers mean bigger files

Image Image size File size
Full size image @ 300 dpi 8″x10″ 1664 KB
Same size @ 72 dpi 8″x10″ 77 KB
Right sized @ 72 dpi 3″ wide 36 KB

That’s a 98% reduction in file size just for picking the right sized photo!

Printed images generally require a resolution of at least 300 dpi. And that makes big files. (It might be a small image size, but the file is big. Make sense?)

Most computer screens can only show images at about 72 dpi. So if you’re making a file that will only show on the screen, and you’re aiming for a small file, then high resolution doesn’t buy you anything. Set the resolution of the image to no more than 72 dpi.

  • Consider Form vs Function

If you are producing a document suitable for framing (so to speak), you want the highest resolution you can manage.

But if that PDF is likely something people will read on the screen, or print out, read, and then toss, is magazine quality photography important (and do you even HAVE magazine quality photos in the first place?)

  • Test to see how low a resolution you can tolerate in the final product.

If you’re putting this low resolution image into a document that will be converted to PDF, print yourself a test copy and see if you can tell the difference. If you can’t, maybe you don’t need such a magnificent image.

And if you figure people are just printing these out at  home to read and toss? I’d use 72 anyway (or perhaps 90  although I wouldn’t bother)

  • Other ways to reduce PDF file size

Check the PDF printer settings. Select the one for “Smallest File Size.”  Again, print yourself a copy from the PDF and see if it meets your needs.

Save with the file as few different fonts as you can manage when you save to PDF.  On a general low end program that does “Print to PDF” you probably can’t control that. But if you can, then just take what you need.

Does this help?  I hope so.
Have questions? Please ask.  There’s a big box for that below.


Author: Kerch McConlogue

Harrisburg, PA: A WordPress front end web developer who speaks plain-English to nonGeeks

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