Is it a Illustrator file link? Or created in Indesign Itself?
Along with the information asked by KK, please let me know what is the format of this link file that you have placed in InDesign.
Also, its effective PPI, you can check this in the links info pallet. This may happen when you actual image size is very small than its output size.
The file is a jpeg, saved from Google, then imported through File > Place .. Same as the other two images in the document, which are even smaller in size, yet importing completely fine ..
Maybe you enlarge the photo.. so the effective resolution increased tends to low resolution in PDF output
When you export to PDF the Compression tab allows you to set the amount of image compression and whether images are down sampled or not. There is an option to turn off down sampling or increase the target resolution.
Whenever I go to 'Create Outlines' prior to a PDF export, one of the images in my document isn't having outlines created for it, and as such, once exported, is appearing low-res ..
If I understand your post, you are expecting Create Outlines in InDesign to convert raster graphics into vector ones. That is not what it does, and it is generally a bad practice to apply it to all the content in a document. Create Outlines has no effect on anything except for text - it turns it from live text into static shapes (destroying much of the special formatting, such as auto numbers and bullets, underlines, text box color, etc. in the process).