Thanks. Unless PDFs have heavy compression they tend to be too large to upload.
It would be really useful if someone could describe the processes an images goes through on upload. I can them (hopefully) adjust accordingly.
My apologies for the delay in replying - I'm slowly catching up on posts after a couple of weeks holiday.
The software should limit the size of any images to a maximum of 1500px x 960px and resize appropriately if any larger. This has been refined over the years as a suitable compromise for those on a slow internet connection to provide a reasonably responsive page loading and yet also allow a reasonable resolution to view fine detail in the photos.
Attachments in general are limited to 10Mb is size - unlike images they are not displayed inline on the posts but appear as a download link in the post. So the larger attachments do not slow down the loading of the pages but the end user can make a conscious decision to download the file by clicking on the link. This includes pdfs documents.
The thing with pdf documents is that it was originally designed as a
Portable
Document
Format (hence pdf) and if you open them in a text editor you can see internally it has it's own text markup language and vector imaging system which can be compressed. So when you convert a word document to a pdf then it can be compressed by a significant amount. Unfortunately it cannot convert images, jpeg, png etc. so they are simply embedded in the pdf, this means that when you convert an already highly compressed image file to a pdf it is unable to compress it any further so a pdf from an image is often larger than the original image as it has a little of the pdf markup wrapping around the image.
So if the generated pdf is less than 10Mb in size then you should be able to attach it. Alternatively I would look at the specific application you have used to generate the technical drawing - unless of course they are just photos of a paper drawing. If it's a drawing package then can you export directly to dxf or pdf format? i.e. skip the image stage - frequently these will be smaller than the image file and are amenable to compression. Finally if it exports to a different format then please let me know which format and I can look into tweaking the attachment settings to allow other formats, I've done this previous for SketchUp files (*.skp).
Regards