We tried a lot of different designs and although some increased the size, strangely some also ensured the PDF created was smaller. We’ve seen this most frequently when using PowerPoint’s ‘Design Ideas’ feature (Design > Design Ideas on the ribbon) as shown above - but there are undoubtedly other image treatments that may trigger this issue. This issue seems to be triggered by only certain images and image effects used in the original PowerPoint file, which can trip up the conversion. To test this theory we created a simple presentation containing one slide, with a single 6.2 MB JPEG image, resulting in a 6.3 MB PPTX file, which you can see here: So for example, a single highly compressed JPEG image in your PowerPoint file can easily double in size when it is exported to the PDF and saved using Flate compression. Under certain circumstances some images which are saved as JPEG in the source presentation, are encoded into the PDF using a lossless compression format called Flate when it’s used in PDF files (its official name is Deflate).īeing lossless, Flate retains all of the image information but the downside is that the image size will be a lot bigger. We discovered that the main reason for bloated PDF files created from PowerPoint appears to be due to a little-known limitation of the PDF creator on Mac (“Quartz PDFContext”). Why are some PDF files bigger than PPTX on Mac? So we decided to run some experiments and share the results. On closer investigation we came to realise that something a little odd was going on. They had to compress it again with NXPowerLite before they could email it.

They had compressed their PowerPoint file before exporting it to PDF and had been surprised to find the PDF was much larger.

We first heard about this from a customer who had been troubled by this problem, and thought it might be an issue with our compression software NXPowerLite. In this post, we attempt to demystify this strange occurrence and give you some tools to help when it happens to you. Sometimes you might experience an unexpected, and occasionally dramatic size increase when saving your PowerPoint presentation as a PDF on Mac.

How to convert pptx to pdf on mac