Today we continue the series about PDF, and often we need to make large files smaller and easier to share. To reduce the size of pdf files we basically have 3 options: your own actions while creating a file, saving an existing file in lower quality, or compressing a file through special online tools. The first one is self-explanatory, so let's review the rest.
There's also a video version of this guide, if you prefer it that way, check out our How to reduce PDF file size video on YouTube.
Options in your PDF viewer app
You don't have to start searching for external tools to reduce file size right away, there are options for this in the PDF viewer/editor app you're using. One of the simplest steps is re-saving the file. Most probably you have Adobe Acrobat so let's start there.
For the purposes of this review I got this "Life And Style Weekly" magazine, which is large in size specifically - 54 pages and 70 Mb total file size - so we can see how much smaller we can get it in the end. For example, if I'd want to send it in email to a friend, it would be impossible, since most email services have a 25 Mb attachment size limit.
So, I've opened my pdf, now click File, in a dropdown menu choose Save as Other, and then Reduced Size PDF. You'll be prompted to select the version compatibility for Adobe Acrobat, or just leave it to the default "Retain existing" setting if it does not matter to you. Click OK and save it. I'll save it as a different file, so we can see the difference. So it is now 67 Mb… well, not far off from 70 Mb original size.
But we have a better, more advanced option, called PDF optimizer. Similarly, go to File - Save as other - and then Optimized PDF. And there's a whole menu, let's dig in. It has 3 setting modes to start with: Standard, Mobile and Custom. And then it has this button "Audit space usage" which is a place I recommend to begin with so you can first review which elements are making up the most data, and then optimize accordingly. In my case, I see that images take up 99% of space in my magazine, so my priority would be obvious.
We see that PDF optimizer presents several areas: images, fonts, objects, user data, and clean up - each with independent options in it. I'm paying attention primarily to images, and Adobe offers several configurations for downsampling images:
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Downsampling method (average, subsampling, bicubic)
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PPI settings - or "pixel per inch" ratio, that is setting the images that are above X ppi to the desired ppi
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File format - JPEG, ZIP, or retain existing
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Quality - from maximum, high, medium, to low and/or minimum
There's also a distinction for color, grayscale and monochrome images. I'm setting images to low quality and re-saving the document. 67 Mb… hmmm, not enough clearly. Let me quickly go back and set the optimizer tool to the Mobile setting to check for a difference. The same file size, so the efficiency of this Adobe tool is doubtful to me, although if a pdf is not 99% images like mine, the results could be different.
As an alternative, I will check with another pdf application, for example PDF XChange which I like for flexibility and ease of use. I open my magazine, go to File, and there we have "Save as optimized". Essentially the same menu as in Adobe Acrobat - images, fonts, objects, user data. In user data I'll probably discard everything - links, metadata, comments, layers, print settings etc.
I will also choose the minimum quality for images this time, and save. 4.6 Mb - wow, I definitely was not expecting such reduction, which is about 90% of original file size. Much better compared to Adobe. Now I'm curious how that file looks and whether it is readable after such a drop. Yeah, the quality of images is visibly poorer, but still viewable I'd say. Fonts and text are readable as well.
So, that was the first general way of reducing pdf file size. If it's not enough for you, or say you need to process multiple files, we have the second way - online pdf compression tools.
Online compression tools (for free)
Online tools to reduce (or also referred to as 'compress') PDF file size are arguably the easiest option. Straightforward principle - drag-and-drop the file, choose compression level, and download. Most of them are free, which is also good news, albeit you'll see some ads while there which is tolerable. And we can use it on any device, PC, laptop or a mobile phone.
Let me go through several tools so you get the idea and maybe we should also then compare their results. I'll probably just take the first 5 tools from the Google search - "reduce pdf online". And I'll start with Adobe which is always the primary service when it comes to any pdf-related tasks.
As you see it's a single-task interface so you won't miss or get lost - just select a file and load it. Here's my magazine 70 Mb in size. After it is uploaded, select the compression level - 1 of 3 available, high, medium and low. Displaying the estimated size for each mode is also useful, so that users can make a better choice. I'll go with Medium which should be around 22 Mb… and processing takes a while… ready, and we see that the actual size is 28.8 Mb which is not far off, and from 70 to 28 is decent. Now download and let's see how it looks - Ok as for me and text is readable. I'll go back to see if I can process multiple files at once - no, I can't.
The next one is iLovePDF. It has the same interface, yet there are 2 additional options along with selecting a file from your hard drive: from Google Drive and Dropbox, which could be helpful for sure, if you store pdf files there. I'm adding my 70 Mb file and I see that I can add more files too, so let's test it with multiple files. We see that the free tool is limited to 200 Mb per task - fair enough. The usual 3 compression levels, so I'm going with the standard one and clicking Compress. The file is automatically downloaded and data is displayed about the results: 88% saved, and this is actually so, since my file is only 9 Mb now. I'm also curious about the highest level - and now the file is 5 Mb, which is 93% compression. I can also delete my file from iLovePDF server instantly, instead of leaving it as is, while their policy is 2 hours before removal. This is a great feature.
Moving on to the 3rd one and that is SmallPDF and it claims to be able to reduce the size of files up to 99%. But let's see. So choose the file, let it upload, then choose 1 of 2 compression levels - basic or strong. Basic level estimates to reduce my 70 Mb magazine to 42 Mb, while strong level down to 17 Mb. I'm going with Strong. Now SmallPDF displays the preview of my file, and to the right it provides Export, Download and Share options, and some more editing tools. Exporting in other formats - here Word, Excel, Powerpoint or JPG - is a great extra feature not all pdf compression tools have. Ok, I'm downloading my file and it is even less than a given estimate - 7 Mb. Another excellent trait is batch processing, it seems that SmallPDF has no limit on multiple files at once, for example I'm testing this out with 17 pdfs and it starts uploading and compressing 5 at a time, until all files are processed. This is superior to any other online pdf tool which usually allows 2 or 3 files simultaneously.
The 4th online tool on my list is PDF2Go. Users can select files from their computers, Google Drive or Dropbox. Let me try multiple files right away - I see that in the free version only 2 at a time are allowed, for more you'd have to purchase the Premium plan. Now I'm adding my test pdf - the upload speed is actually rapid - it takes literally 3 seconds. Then we have 3 modes of compression - basic, strong and custom, consisting of 6 presets that are based on image quality - from as low as 20 DPI to as high as 300 DPI. I will choose the basic mode, wait, and get my file down to 10 Mb. Briefly checking it - it is pretty alright. But I'm also curious about a low quality 40 dpi preset, so I'll redo the file - now it is down to 2.8 Mb, that is compressed by 95%... but how does it look? Yeah, quite ugly I should say. Overall, for simple tasks of reducing a pdf size - PDF2Go will do.
Ok, one more tool and that will be enough - Online2PDF. Interface is a bit dated but nevertheless. Next to the Select button we see the info about file size limitations: maximum size per file is 100 Mb, 20 files per session allowed, and the total size limit for multiple files is 150 Mb. This is less than in other online tools, yet casual use with some office documents will be no problem. When it comes to compression, Online2PDF deals with images - users will set 3 parameters - quality, resolution, and color. Quality ranges from 0 to 10, with basically 4 levels: low, medium, optimal, and high. Same with resolution, presets ranging from 25 to 1200 dpi, though such maximum DPI seems unnecessary when you are trying to reduce the size not increase it.
I'm setting Medium for both parameters, and in Color I'm leaving it color, not black-and-white. The next fine feature is converting to other formats, and there are plenty - Word, Excel, JPG, PNG, RTF, EPUB. There's also protection - meaning that users can set a password to open a file, or lock it for printing/modifying only. You will see ads while waiting for processing. The resulting file is 9 Mb from 70 in my case.
Of course, there are dozens, if not more, of other great pdf compressors online… PDF Candy, Sejda, Foxit, Duplichecker, XConvert, PDF4Me among them. But at this point you get the idea, so no need to go through all of them.
Summary
So, as we see when it comes to reducing the size of a pdf file or document, this should not be a problem these days, since we have plenty of options. The most effortless one is online tools and this way you can bring down the size of files drastically - 100 Mb to 10 Mb is possible, and even more if you really have to.
In regards to my top-5 picks as suggested by Google, I've made a little comparison with several parameters, including results from my test pdf. Let me preface the table below with the following. Compression of my pdf was performed in standard (or basic) mode in each tool. The original test file size is 70 Mb.
From it, we see that 2 tools - iLovePDF and Online2PDF - provide bigger reduction rates, both 88% drop. File size limits in all tools are raised pretty high (1/2/5/8 Gb), except for Online2PDF with 100 Mb, although even that is enough for most files. SmallPDF stands out due to the ability to process big numbers of files simultaneously, option to convert to other formats and other extra tools.
Last but not least, a word of caution about online pdf compressors. If you've got a pdf document with private, corporate or commercial information - it would be better not to use online tools due to the risk of leaks.
So, all for now. If you have any suggestions or questions on the topic, feel free to leave a comment below. Have a nice day, everyone!