The short answer
Two routes, in order. First, compress: drop the PDF into the compressor with image quality around 75%, and a typical scan shrinks to a third or a fifth of its size. Second, split: still too large? Cut it by page ranges and send the parts. Neither needs installed software — everything runs in the browser. But compression has a cost most people never hear about; read section three before you ruin your archival original.
Why your PDF is so large
The culprit is nearly always scanning. Scanner apps default to capturing each page as a 300 dpi image — one A4 page costs 500 KB to 1 MB, so a fifty-page contract blows past 30 MB. A text-born PDF (say, Word's "save as PDF") is usually a few hundred KB because it stores text codes, not pictures. The test is simple: try selecting a sentence. If you cannot — or a single drag grabs the whole page — it is an image-type scan, exactly the kind that compresses best.
First find out which number is blocking you
"Too large" means different things per channel: chat apps cap individual files, email attachments commonly sit around 50 MB, and government or business portals range anywhere from 10 to 100 MB. So check the receiver's limit first — it is printed on the upload page, or in your mail provider's docs; when unsure, aim for under 50 MB. The goal is "inside the limit", not "as small as possible" — chasing tiny sizes just burns quality for nothing. And if the receiver also restricts formats, confirm the extension survived the trip.
Move one: compress, starting at 75%
Open the PDF compressor, drop the file in, set image quality to 75% — the sweet spot for scans: text and stamps stay crisp while the size usually drops to about a third. Need it smaller? Step down to 65% or 60%; low-stakes archives read fine even below 60%. Internally each page's image is re-encoded, so lower quality means smaller files. One caveat from the tool page itself: this method redraws every page as an image — perfect for scans and picture-heavy PDFs, counterproductive for text PDFs, which are already small and may even grow.
Move two: split by page and send in parts
If compressing is not enough — or you refuse to trade clarity — split. Cut the file into page ranges: an 80-page bid document becomes four 20-page parts. Often the receiver only needs pages 3 through 8 anyway; extracting exactly that range does them a favour. Name the pieces "original-001-020.pdf" style so the order is obvious and the receiver can merge them back if needed.
The cost of compression: keep the original
Because compression redraws pages as images, text stops being selectable and searchable. Fine for human eyes, painful if the file later goes through a workflow — annotations, quoted text, OCR archiving. The habit that saves you: originals live untouched in an "originals" folder; compressed and split copies are send-only duplicates. If you split, consider merging the range back into one clean file before sending so the receiver does not get fragments.
Three checks before sending
One, the size: confirm the final file size in its properties, not the tool's on-screen estimate. Two, the content: flip through a couple of pages, especially signature pages, stamped pages and anything with amounts — heavy compression blurs exactly the pages you added last. Three, completeness: for split sends, count the parts and check the page ranges connect; open them in order yourself once. For documents containing ID numbers or bank details, consider retracting or deleting the chat message afterwards.
想马上动手：用 PDF 压缩 把扫描件瘦下来，超限就上 PDF 拆分 按页切开，碎片用 PDF 合并 收拢；顺带可以用 PDF 加密 给敏感材料加一道打开密码。Try it now: shrink scans with the PDF compressor, split oversized files with the splitter, stitch pieces back with the merger, and lock sensitive files with PDF encryption.
FAQ
Will the compressed PDF look blurry when printed?
At 75% quality a scan prints essentially identically — print resolution is more forgiving than what you need on screen. The test is the source: if the original scan is sharp (clean text, solid stamp), 75% holds up; if the original was scanned badly, the blur was already there and re-scanning beats re-tuning parameters.
The PDF used to let me select text, and now it does not.
Expected: compression redrew each page as an image, so the text is now "painted on". Use this compression for image-type PDFs and for files meant to be read, not processed. Text PDFs are small anyway; if one really needs slimming, look for the embedded images and handle those instead of redrawing the whole file.
Can I compress and split on a phone?
Yes. Everything runs locally in the mobile browser: open the page, pick the PDF from your files, download the result and forward it. Large multi-page files take from seconds to a minute depending on the phone. And because processing is local, sensitive documents — contracts, IDs — never leave your device.