How do I get a high resolution pdf file in InDesign

[nreynolds8708]

I have created an ad in InDesign that is going into a magazine. They are requesting a high-resolution file (300 dpi). The ad I have created is a 68mb. When I create a pdf file to send to the magazine the file size is now 1.3mb. I am using Adobe High-Quality Print preset when exporting. What am I doing wrong? It needs to in a much higher resolution than 1.3mb.

I am on a MacBook Pro. InDesign CC 2019

[BobLevine]

What makes you think you're doing anything wrong?

[Dave Creamer of IDEAS]

Most likely, the magazine was requesting that RASTER images are at 300 ppi--not the entire PDF. The PDF typically keeps any Illustrator graphics* and any InDesign elements (including text) as vector. Vector elements compress very small.  Only raster graphics have resolution (in the manner we are speaking of). High Resolution is not always related to an exact file size in a PDF--and a PDF size in not related to the InDesign file size.

*Illustrator files can contain raster graphics/items too.

[nreynolds8708]

Thank you for responding, a little too technical for me to understand. It just seems odd it goes from a 64mb file to a 1.3mb file. 

[Dave Creamer of IDEAS]

Did you get any other information/requirements besides "300 dpi"?

[rob day]

The [High Quality] preset compresses images on export, see the Compression tab in the Export dialog. It will also resample images with a higher Effective resolution than 450ppi—if you have scaled your images down their Effective resolution would proportionaly increase. A 300ppi image scaled to 50% would have an Effective res of 600ppi, and would get down sampled on export.

Also, the [High Quality] preset is not ideal for print, one of the PDF/X presets would be better for offset printing.

[rob day]

JPEG compression, which is used by default with most Export presets could easily compress by the amount you are seeing. The final compression depends on the image content. This 57mb Photoshop file compresses to 2.9mb because there are a lot of repeating pixels—the compressed file size doesn't relate to image resolution: