You asked why some documents in BSOL can’t be downloaded in PDF, and why some documents are not included in subscriptions.
Some documents, such as BS 7671 (IEE Wiring Regulations), have a copyright which is shared between BSI and other publishers. These documents cannot be downloaded via BSOL due to the restrictions of the shared copyright. You can still search and find these documents in BSOL, and are subsequently available to purchase outside of your subscription.
Some other documents such as colour charts are excluded from download, as displaying these colours on uncalibrated monitors or printing from uncalibrated printers would inaccurately represent the content of the standard. These are only available in hard copy to ensure fidelity of the colours represented in the standards.
