No particular document is required for a PR to enter Canada. But the PR must establish identity and status. Establishing identity, especially when by presenting a passport which is already associated with the individual's IRCC client number, usually suffices to establish status. This may require a referral to Secondary, but for most people this would be a relatively simple and brief referral. Unless some other issue is involved (suspected breach of PR RO for example), all that needs to be done is a fairly simple computer-based verification of identity and status. And once this has been done, near-future trips across that same border crossing, particularly if using the same vehicle and it is owned by the PR, should result in being waived through without a referral to Secondary . . . subject to incidental reasons for a referral, and of course for a reasonable period of time until a PR card is obtained.
Very few referrals to Secondary for immigration purposes are random. Overwhelming majority of referrals to Secondary are criteria based, subject of course to the personal application of the criteria by the individual PIL officer conducting the Primary Line Inspection interview.
Foremost observation: Reason why the PR does not have a currently valid PR card is a big factor in how things will go at a PoE when seeking entry into Canada. Beyond that, the PR’s circumstances and history are also big factors. There will be a reason for the referral.
Presenting an expired PR card and passport is better than presenting CoPR and passport. For many in this situation (PR card expired, waiting for new card to be issued), their circumstances are not complicated, and while they may be referred to Secondary this should not be a difficult or lengthy affair so long as, of course, they are settled in Canada and there is no indication of any issue about compliance with the PR RO. Subsequent crossings at the same PoE and in the near future should go easily without any additional referral to Secondary. . . . really helps if the traveler is driving the same vehicle, especially one registered to the traveler, each time.
For new PR who has not yet been issued a PR card, first trip back may similarly result in a minimal Secondary referral but subsequent travel across the same land border crossing should be incident or referral free . . . again, really helps if the traveler is driving the same vehicle, especially one registered to the traveler, each time.
Obviously, though, any PR with potential issues, or (other than a new PR) who is not well settled in Canada, or whose compliance with the PR RO is open to questions, faces a much higher risk of the Secondary referral.
Obviously, travel via the U.S. from beyond the U.S. will increase the risk of a Secondary referral (for a PR without a valid PR card).
There are scores of particular factors which can trigger the referral to Secondary.
But the main factors which determine whether there is a referral to Secondary (for immigration purposes) are tied to:
-- who the traveler is
-- the traveler’s status
-- the identification or status documents or Travel Documents the traveler presents
-- the traveler’s immigration history
-- the traveler’s border-crossing history
-- the traveler’s demeanor when responding to the PIL officer’s questions
-- the content of the traveler’s answers, taken in context (including all the above)
-- FOSS notes or alerts regarding the particular traveler
-- the traveler’s means of transportation, also considered in context
The PIL officer’s role is not to make conclusive judgments about the traveler, but rather it is simply to identify if there is a reason, under the criteria-in-force, to subject the traveler to further examination prior to being allowed to enter Canada. For determining who is referred, the bar is quite low, but nonetheless high enough that the vast majority of travelers are not referred to Secondary for immigration purposes. But then again, the vast majority of travelers entering Canada are either Canadian citizens or Canadian PRs (both of whom are entitled to enter Canada) or U.S. citizens (who are routinely waived into Canada), and they present appropriate documentation establishing both their identity and their status.
Incidental factors include criteria-of-the-day (or week, or month, or such), which can be implemented by CBSA across the board, or just in certain regions, or even a criteria-of-the-day for a specific PoE.
Incidental factors include the biases and intuitions and propensities of the individual PIL officer conducting the Primary Line Inspection interview.
Incidental factors can include alerts among other things which can lead PIL officers to pay particular attention to certain types of travelers or certain circumstances, and so on.
All that said, unless the particular PoE is especially busy, or it is a slow time with minimal staff on duty such as late night or early morning, or there are language issues, even if the examining officer in Secondary needs to do some research to verify identity and status, the PR who presents a passport previously used when interacting with IRCC should encounter only a brief delay, not hours, with some exceptions (concerns based on photo versus individual’s appearance for example). And obviously, any PR for whom there may be PR RO compliance concerns, there could be related questioning and potentially procedures if the Secondary officer concludes there was a breach of the PR RO.