Join Anne-Marie Concepción for an in-depth discussion in this video Building smaller PDFs with the same content , part of Acrobat X Tips and Tricks.
When your PDFs are going to leave the realm of professional publishing, when you need to distribute them to regular end users who might only have Reader, maybe an older version of Reader at that, maybe a slow connection to the Internet, or a computer with not enough RAM, you need to try and optimize your PDFs for those users, because nothing is as frustrating as clicking a link to a PDF on a Web site, and then saying, oh, this will take approximately 45 minutes to download. So one of the first things that you can do with any PDF is gauge its current size, and try and reduce the file size, without affecting the quality of the PDF to any significant degree.
So, we are looking right now at an 8 page newsletter done by the Chicago Creative Coalition; an association in Chicago. Now, this PDF was not created for downloading from their Web site, even though, actually, that's where I got it from. This PDF -- I can tell, because of the crop marks -- was actually created for printing. And in fact, if we go to Tools, and go to Print Production, and Output Preview > Object Inspector -- you don't have to do all this, but I just want to show you that if I click on some of these images, the resolution is pretty high. 750 pixels across, 967 pixels across, meaning the resolution is 967 ppi.
Probably because these were high res images that were then scaled down after they were placed in InDesign, which in effect, makes the pixels even smaller, increasing the resolution. In other words, we don't need all of this pixel information when we are just going to read it on screen; probably don't even need it for print either. And that is probably why this PDF is so large. We can immediately tell the size of the PDF by going to the File menu, choosing Properties, and in the first tab, Description, come down here and look at File Size.
This is 6.49 MB, which is pretty large. So I am going to cancel out of here. How can we reduce the size of this PDF? One way is by going to File > Save As, and choosing Reduced Size PDF. This is a nice fast way to reduce the size of any PDF. It asks, which version of Acrobat should it be compatible with? And the default is Retain existing. That is the one that you almost always want, because that will result in the smallest file size.
I know that a lot of people will be tempted to say, well, I don't need Acrobat X; Acrobat 4 should be fine, and I remember back in Acrobat 4, it could hardly do anything, so that should be a much smaller file. Actually, it kind of works against you, because in some ways, Acrobat will need to tear apart the file in order to be understood by an earlier version of Reader or Acrobat, resulting in a larger file. So if possible, always keep it at this one: make compatible with Acrobat X or later, which is Retain existing; whichever one it is at this moment.
So we will just say OK, and I will save this out to the Desktop. We'll say Reduced, for reduced file size. We get a little warning that says, The PDF document contained image masks that were not downsampled. You are going to get that almost every time, if you have any kind of masking, or cropping going on. And now we are looking at the reduced one. Let's look at Properties to see what the new file size is. 1.12 MB; that's fantastic! The other one was 6 point something, right? So that's one way, is by choosing reduced file size.
You don't have much control over what exactly it's doing, but it does a pretty intelligent job. I am curious to see what it did to these images. So I am going to go back to Output Preview, Object Inspector, and click. Ah, it brought that to 150 resolution. Do you see that right there? And this one is well; interesting. So let's go back to the original one that we had, right here, and we'll double check Properties. Yes, 6.49. I just press Command+D or Control+D to bring Properties up.
Now let me show you another way to reduce the file size that gives you much more control over what's going to happen, and that is to save it as an optimized PDF. You go to the same location as reduced file size. You go to File > Save As > Optimized PDF. I think you can see that the reduced file size did exactly what this setting is saying. It found any images that were over 225 pixels per inch, and it reduced them to 150 pixels per inch, and it made them compatible with the existing level of PDF.
Those are the standard settings, but you can have many other settings. You can save them, and you can switch among them, and you can also change these. Like for example, if you didn't want the images brought down that much, you could say, bring these down to 250 for any images that were over 375; it automatically calculated that. I am just going to say 300. You could also change the Compression from Medium to Low to even save more room, or you could say, keep the compression High. Under Fonts, you can unembed fonts if you want to, because all these are subsets of the fonts that the user chose to embed when they exported to PDF.
Embedded fonts do add to the file size, so you might want to select these, and unembed them. If the documents have live transparency, you could choose to flatten the transparency with certain resolution levels. You can choose to discard things like form fields, you can convert smooth lines to curves, get rid of any tags; some of these are pretty drastic measures, but you can get something really small. And then Discard User Data; you can discard any comments, or forms, or multimedia.
External cross references, if there are any file attachments, get rid of that. And then just general cleanup kind of things; discard invalid links, and so on. But one of things that I like to do when I go to PDF Optimizer is go immediately here to Audit space usage. I wish this were a command that was more readily accessible somewhere else in Acrobat, rather than buried in the PDF Optimizer dialog box, because it's so useful to find out what exactly is contributing to the size of this PDF. When you click it, it goes through the active PDF and it says, well, the Images account for 93% of the file size of this document. And then Content Streams, which usually means the tracking of articles and such, this much. And those embedded fonts only account for about 2% of the file size, so it really wouldn't have done much good to unembed the fonts without reducing the resolution of the images, and so on.
So, Audit space usage is usually very illuminating. Let's go ahead and I am going to choose Standard, and under Images, we are going to make them even smaller. Let's bring them down to 72 pixels per inch, and we will leave everything else the same. And I might save this as reduce to 72 ppi, in case I want to use it again. Then click OK. Now it wants to know where to save it, and now let's call this one -opt, for optimized. And got that same alert as before.
It still looks pretty good. I can see a little bit but of blurring, definitely, but let's check out the file size. Drumroll effect, please. 642 KB; about half the size of what reduced file size did, which makes a lot of sense since we kind of halved the resolution, right? So, two different ways to reduce the file size of your PDFs. One is really quick with Save As Reduced File Size. The other one gives you more control, and that is Save As Optimized PDF.
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