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Why do some pptx lose weight as pdfs while others don't?

Teresa Pascarelli 0 Reputation points
2025-12-11T09:01:45.0366667+00:00

Hello, I need a to convert 2 a pptx slide presentations into pdf files that do not exceed 1 MB. One of them (34MB) reduced to 756KB. The other pptx (40MB) when saving it as a PDF doesn't reduce below 4.8M. Why? it is only 6MB heavier than the other one?

Thank you so much! Teresa

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  1. Restee Miranda 14,040 Reputation points Independent Advisor
    2025-12-11T20:23:49.5266667+00:00

    Thanks for posting to the forum, Teresa.

    The big difference usually comes down to what’s inside the slides. When you save as PDF, PowerPoint compresses text and vector graphics really well, but large, high-resolution images or embedded media don’t shrink much. If your second file has lots of photos, gradients, or non-vector elements, that explains why it’s still heavy. A quick fix is to check the image resolution in PowerPoint under File > Options > Advanced > Image Size and Quality, and set it to compress pictures to 150 dpi before exporting. Also, make sure there aren’t hidden objects or unused masters adding weight. Do you know if the second deck has more photos or detailed graphics compared to the first? Or maybe embedded videos?

    Best,

    rez

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  2. AI answer

    2025-12-11T09:01:59.8+00:00

    The difference in file size when converting PowerPoint presentations to PDF can be attributed to several factors, including:

    1. Content Complexity: The complexity of the slides can greatly affect the file size. Slides with high-resolution images, embedded videos, or intricate graphics will typically result in larger PDF files. If one presentation has more complex content than the other, it may not compress as efficiently.
    2. Image Compression: During the conversion process, the way images are compressed can vary. If the conversion settings prioritize image quality over size, the resulting PDF may be larger. You might want to check if there are options to adjust image quality or compression settings during the export process.
    3. Fonts and Styles: The use of custom fonts or styles can also impact the size of the PDF. If one presentation uses more fonts or complex styles, it may lead to a larger file size.
    4. Slide Count: The number of slides in each presentation can also play a role. A presentation with more slides will generally result in a larger PDF file, even if the individual slides are less complex.

    To reduce the size of the larger PDF, consider optimizing images, reducing the number of slides, or adjusting the export settings to prioritize file size over quality.

    AI-generated content may be incorrect. Read our transparency notes for more information.

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